How do you conjugate a phrasal verb?
In a sentence, what will be correct?
a) The most of its vital part takeS placeS in the park
b) The most of its vital part takeS place in the park
c) The most of its vital part take placeS in the park

and, if I have to put in in past sentence, how would it be?

Question

How do you conjugate a phrasal verb?
In a sentence, what will be correct?
a) The most of its vital part takeS placeS in the park
b) The most of its vital part takeS place in the park
c) The most of its vital part take  placeS in the park

and, if I have to put in in past sentence, how would it be?

Answer

You only conjugate the verb part of a phrasal verb.

Take place, takes place, took place, had taken place, is taking place...

Answer

Not sure what you are trying to say here. Those aren't natural sentences.

Most of the essential action takes place in the park.

In the past:

Most of the essential action took place in the park.

Put is the same in present, past and past participle.

*I put up the shelf"

Answer

Cierto, suena mal.
Esto viene de unos apuntes que hablaba mi profesora de fonética inglesa. Ella querría decir sus partes más importantes en cuanto a su funcionamiento (de algo), solo que he puesto en el parque para que tuviera sentido la frase.
VITAL PART= parte más importante.

Entonces en inglés cómo sería? :O

Answer

I am sorry if I ask you what vital part means? I speak spanish like you and when I saw this I think. Vital part -> parte vital but even in spanish I don´t know what do you mean with vital part. For me "parte vital" significa una parte del cuerpo o de algo que es esencial o muy importante y que sin ello el cuerpo o el objeto no podría existir. Osea que traducido al español seria: La mayoria de sus partes vitales toman lugar in el parque. Suena extraño para mi.