Learn Hardcore Spanish (Spain): Apunta la cita en tu agenda para que no se te olvide. - Write the appointment in your planner so you don’t forget it.

Yes. Apunta is the affirmative tú imperative of apuntar. In -ar verbs, the affirmative tú command coincides with the 3rd‑person singular present indicative form.

tú (affirmative): apunta
usted: apunte
vosotros (Spain): apuntad
ustedes: apunten
Negative tú command: no apuntes (subjunctive)

Spanish normally drops the subject pronoun, so there’s no tú.

What does apuntar mean here? Is it “to aim”?

Here apuntar means “to write down / note.” It can also mean “to aim,” but with things like la cita en tu agenda the meaning is clearly “write down.” Near‑synonyms:

anotar: very common, neutral.
escribir: general “to write.”
In Spain, apuntarse algo can mean “to jot something down for oneself” (e.g., Apúntate mi número).

Why is it para que and why is olvide in the subjunctive?

Para que introduces a purpose clause and requires the subjunctive. The clause expresses a desired outcome, not a fact. Hence (para que) no se te olvide uses present subjunctive olvide, not indicative olvida/olvida.

What does se te mean in no se te olvide?

It’s the combination used with the pronominal verb olvidarse:

se: the pronominal marker of olvidarse (“to get forgotten”/“to slip one’s mind”).
te: the indirect object (to/for you), marking the experiencer. Literal structure: “that it doesn’t get forgotten to you.”

Who is the subject of olvide? Why not olvides?

The subject is the thing that might be forgotten: here, la cita (understood from context), so the verb is 3rd person singular: olvide. If you used olvides, the subject would be tú (“that you don’t forget”), which is a different construction.

Could I say para que no la olvides or para que no te olvides de la cita instead?

Yes, both are correct, with slightly different framing:

para que no la olvides: uses non‑pronominal olvidar with direct object pronoun la (la cita).
para que no te olvides de la cita: uses pronominal olvidarse de with reflexive te. Your original (para que no se te olvide) is common and slightly less “blamey,” focusing on the appointment “slipping your mind.”

Can I use an infinitive instead of para que? Like para no olvidarla?

Yes, since the understood subject is the same (tú):

para no olvidarla (with la = la cita)
para no olvidarte de la cita (with pronominal olvidarse de) Using para que is also natural and emphasizes the intended result.

Why is it en tu agenda, not a tu agenda?

Spanish typically uses en to indicate where you write something: apuntar/escribir/poner algo en un cuaderno, en la agenda, en el calendario. A would indicate direction toward a person/place, not the surface or container where you write.

Does agenda mean “agenda” like in English (a plan or political agenda)?

No—false friend alert. In Spain, la agenda is your paper or digital planner/diary. For a list of topics to discuss, you can say orden del día; for a political agenda, context makes it clear (e.g., agenda política).

What exactly does cita mean here? Could it be a date or a quote?

In this context it’s an appointment (doctor, hairdresser, etc.). Cita can also mean a romantic date or a quotation. A business meeting is usually reunión; a plan to meet a friend is often quedar.

Where do pronouns go with imperatives? Could I say Apúntala en tu agenda?

Affirmative commands: attach pronouns to the end: Apúntala en tu agenda (“Write it down…”).
Negative commands: pronouns go before the verb: No la apuntes en tu agenda. Your sentence spells it out with la cita, which is also fine.

Why is it se te, not te se?

Clitic order rule: with olvidarse, the pronominal se comes before the indirect object me/te/le…. So it’s se me/se te/se le…. Te se is ungrammatical.

Could I just say No te olvides (de la cita) as a standalone reminder?

Yes. No te olvides de la cita is a common negative command (“Don’t forget the appointment”). Your original uses a purpose clause tied to the first action (write it down so that…).

Any Spain‑specific notes about forms?

Yes, Spain uses vosotros for “you all.” The imperative would be apuntad (affirmative) and no apuntéis (negative). In Latin America, ustedes covers you‑plural: apunten, no apunten.

Any accent or spelling pitfalls here?

tu (your) has no accent; tú (you) does. In your sentence it’s tu agenda.
se (pronoun) has no accent; sé (I know / be!) does.
If you attach pronouns to an affirmative command and the stress shifts, add an accent: Apúntala (note the accent on ú).