In French, the preposition “avec” is used to express being or doing something together with someone.
The verb “s’asseoir” (to sit) can be followed by “avec” to mean “to sit with” a person or group.
The context shows that the speaker is refusing to sit with certain people, so “avec” is appropriate.
Examples:
— Je veux m’asseoir avec mes amis. (I want to sit with my friends.)
— Il s’est assis avec ses collègues. (He sat with his colleagues.)
The negative structure “ne... pas” wraps around the verb and its pronoun: “Je ne veux pas m’asseoir...”
So the complete sentence becomes: Je ne veux pas m’asseoir avec ces personnes.