La excursión incluye una visita guiada y tiempo libre para usar el plano de la ciudad.

Because incluye is the 3rd person singular present form of incluir.

• incluir = to include
• incluye = it includes

The subject is la excursión, which is singular, so the verb must also be singular:

• La excursión incluye... = The excursion includes...

If the subject were plural, you would use incluyen:

• Las excursiones incluyen... = The excursions include...

Yes. Excursión is a feminine noun, so it takes la.

A very useful pattern is that many nouns ending in -ción or -sión are feminine:

• la excursión
• la estación
• la información
• la decisión

So even though English nouns do not have gender, in Spanish you need to learn the noun together with its article whenever possible.

The accent mark shows where the stress goes: ex-cur-SIÓN.

Spanish stress rules say that words ending in a vowel, -n, or -s are normally stressed on the second-to-last syllable unless there is a written accent. Without the accent, you would expect a different stress pattern.

So the accent in excursión tells you that the final syllable is stressed.

Una is the indefinite article, so it means a guided tour/visit rather than the guided tour/visit.

Here, the sentence is just listing what the excursion includes:

• una visita guiada
• tiempo libre

Using la visita guiada would sound like you are talking about a specific guided tour already known to the listener.

Guiada means guided.

It comes from the verb guiar, which means to guide. In this sentence, guiada is functioning like an adjective describing visita.

So:

• visita = visit / tour
• visita guiada = guided visit / guided tour

This is very common in Spanish. A past participle can often work as an adjective.

Because in Spanish, adjectives often come after the noun.

So while English usually says:

• guided tour

Spanish often says:

• visita guiada

This noun + adjective order is very normal in Spanish:

• vino tinto = red wine
• casa grande = big house
• visita guiada = guided tour

Because tiempo libre is being used as a more general, uncountable idea: free time.

Spanish often omits the article with this kind of expression, especially in lists after verbs like incluir:

• incluye desayuno y cena
• incluye transporte y alojamiento
• incluye una visita guiada y tiempo libre

In English, this is very similar to saying:

• It includes breakfast and free time

Saying un tiempo libre here would sound unnatural.

Here it means some free time built into the excursion schedule.

It does not mean all of your free time in life in a general sense. In this context, it means there will be a period when participants are free to do something on their own.

So the idea is:

• first, there is a guided visit
• then, there is some free time

Para expresses purpose: for / in order to.

So:

• para usar el plano de la ciudad = to use the city map / for using the city map

After para, Spanish normally uses the infinitive when the action is being expressed in a general way.

Compare:

• Estudio para aprender. = I study to learn.
• Necesito tiempo para descansar. = I need time to rest.
• tiempo libre para usar el plano = free time to use the map

In Spain, plano is very commonly used for a city map or a street map, especially a more practical map used for finding your way around town.

• plano de la ciudad = city map
• mapa is more general and can be a map of a country, region, or the world

So in this sentence, plano sounds very natural because it suggests the kind of map a tourist would use while walking around a city.

Because it is being treated as a specific map: the city map.

Spanish often uses the definite article when referring to something that is understood from the situation or context. Here, the idea is probably the city map given or used during the excursion.

So:

• usar el plano de la ciudad = use the city map

Using un plano de la ciudad would mean a city map, which is possible in some contexts, but el plano de la ciudad sounds more natural here.

It describes el plano.

So the structure is:

• el plano de la ciudad = the map of the city / the city map

It does not describe tiempo libre. The sentence means that the excursion includes free time to use the city map, not that it includes the city’s free time.

So the grouping is:

• tiempo libre
• para usar [el plano de la ciudad]