As the title suggest how do i change a cities faction allegiance to my own once i capture it? Do i build colonists from a native city and just leave them in the foreign city? Do i need to disband the colonists once there?

I wasn't able to find too much info about this process in game or on the forums so any help would be appreciated.

You need colonists from your Culture. You'll need 1 colonist per city level of the desired city.

So, say Rome is Level VI and you want it Etruscan, you'll need 6 colonists. Move them into the city and hit the Colonize button on the bottom right of the city info tab.

Thanks Phalnax! Makes sense now.

Thanks Phalnax! Makes sense now.

Sure, it took me forever to find that button at first even though I was looking for a button for such a task. womp womp.

There is a bug with Colonists though. Instead of being consumed, they are added to that city's recruitment pool allowing you to recruit a new set of colonists and continue doing the same thing without penalty. Don't get used to it...although it is convenient.