La farmacéutica me explicó con mucha paciencia cómo usar la pomada y cada cuántas horas ponerla.

Here it means the female pharmacist.

In Spanish, farmacéutico / farmacéutica can refer to:

• a pharmacist
• or, in other contexts, something pharmaceutical

In this sentence, because it starts with La and refers to a person who explained how to use an ointment, the natural meaning is the pharmacist.

Also, the ending -a shows the person is female:

• el farmacéutico = the male pharmacist
• la farmacéutica = the female pharmacist

Me explicó means explained to me.

Spanish often uses an indirect object pronoun for the person receiving the explanation:

• me = to me
• te = to you
• le = to him/her/you (formal)
• nos = to us
• os = to you all (Spain)
• les = to them/you all

So:

• La farmacéutica me explicó... = The pharmacist explained to me...

In English, we can say explained to me, but in Spanish the pronoun is very natural and usually necessary.

Because it refers to a completed action in the past.

• explicó = she explained
• infinitive: explicar

The sentence is talking about one finished event: the pharmacist explained it.

Compare:

• me explicó = she explained to me
• me explicaba = she was explaining to me / used to explain to me

Here, explicó is the normal choice because it describes a specific completed moment.

Spanish often expresses ideas with a noun phrase instead of an adverb.

So:

• con mucha paciencia = with a lot of patience

This is very natural Spanish and often sounds more idiomatic than trying to copy the English structure directly.

You could think of it as:

• She explained it to me with great patience

Spanish does have adverbs, but in many cases a phrase like con paciencia, con cuidado, con interés, etc. is more common.

Because cómo is an interrogative/exclamative word here, even though it appears inside a larger sentence.

In this sentence:

• cómo usar la pomada = how to use the ointment

Words like these usually take an accent when they introduce an indirect question:

• cómo = how
• qué = what
• cuándo = when
• dónde = where
• cuánto = how much/how many

Compare:

• No sé cómo hacerlo. = I don’t know how to do it.
• Lo hice como me dijiste. = I did it as you told me.

So cómo has an accent because it means how in an indirect question.

Because Spanish often uses an infinitive after words like cómo, qué, cuándo, etc. when the subject is general or understood.

So both are possible:

• cómo usar la pomada = how to use the ointment
• cómo se usa la pomada = how the ointment is used / how to use the ointment

The infinitive version is very common and concise. It works much like English how to use.

Pomada usually means an ointment.

It refers to a medicinal product you apply to the skin. Depending on context, English might say:

• ointment
• sometimes salve
• occasionally cream, though crema is more specifically cream

So:

• pomada = ointment
• crema = cream

In medical/pharmacy contexts, pomada strongly suggests a thicker topical treatment.

Literally, it is something like every how many hours.

This is a very common Spanish way to ask or report frequency in time intervals:

• cada cuánto = how often / every how much time
• cada cuántas horas = every how many hours

Examples:

• ¿Cada cuánto lo tomas? = How often do you take it?
• ¿Cada cuántas horas? = Every how many hours?
• Me dijo cada ocho horas. = She told me every eight hours.

In your sentence, it is part of what the pharmacist explained:

• ...y cada cuántas horas ponerla = ...and how often / every how many hours to apply it

Because horas is a feminine plural noun, and cuánto has to agree with it.

Forms:

• cuánto = masculine singular
• cuánta = feminine singular
• cuántos = masculine plural
• cuántas = feminine plural

So:

• cuántas horas = how many hours

Agreement is essential here.

Because when a pronoun goes with an infinitive, it is usually attached to the end.

So:

• poner + la = ponerla = to apply it / to put it on

This is very common with:

• infinitives: hacerlo, tomarla, usarla
• gerunds: haciéndolo, tomándola
• affirmative commands: hazlo, tómala

With a conjugated verb, the pronoun usually goes before:

• la pongo = I apply it
• la usó = she used it

But with the infinitive poner, attaching it is the normal pattern:

• ponerla

Because la pomada is a feminine singular direct object, so the matching pronoun is la.

• la pomada → la
• el medicamento → lo
• las pastillas → las
• los comprimidos → los

So:

• usar la pomada = to use the ointment
• ponerla = to apply it

Spanish avoids repeating the noun unnecessarily, just like English often uses it.

Yes. Its basic meaning is to put, but in contexts involving creams, ointments, drops, makeup, etc., poner often means to put on / apply.

For example:

• ponte crema = put some cream on / apply cream
• poner la pomada = apply the ointment

So in this sentence, ponerla is naturally understood as to apply it.

Because Spanish can link both ideas to the same verb explicó without repeating everything.

The structure is essentially:

• me explicó
  
  • cómo usar la pomada
  • y cada cuántas horas ponerla

So the pharmacist explained:

1. how to use the ointment
2. how often to apply it

Spanish often avoids repetition when the meaning is already clear.

Yes, but the meaning would be different.

• cuándo ponerla = when to apply it
• cada cuántas horas ponerla = how often / every how many hours to apply it

Cuándo is about the time or moment. Cada cuántas horas is about the interval or frequency.

For medicine, frequency is often more useful, so cada cuántas horas is very natural.

Yes, very natural.

Nothing in it sounds odd for Spain:

• la farmacéutica
• la pomada
• con mucha paciencia
• cada cuántas horas
• ponerla

All of these fit normal everyday Spanish in a pharmacy or medical context.