How do you chose where you want to set a campaign?

hey divas, i've dm'd a few one shots and other non-dnd ttrpg (like call of cthulhu) so i'm not new to being a dm, but i've never done a full campaign in 5e and i want to. i've got a handful of ideas but am struggling to figure out where to set it, like what premade towns, cities, etc. to use. any help would be super appreciated. 

I have access to some of the free books here but don't own any for myself, but if you give me the name to some to look through I'm sure I can find it somewhere. 

Thanks in advance!