If you want to hire a staff writer you can post here or check other sites who do have staff writers, find a writer you like and contact them. I write for a few travel blogs and other blog owners come to find me thanks to my written work.
If you want to become a staff writer, find a blog you like, and pitch them your ideas! If they already have staff you may have to wait until a spot is vacant, if they don't they may think about it for a while before hiring. Any way, unless you find a post from a blogger asking for staff writer, chances are you'll have to try a bit before you succeed. Good luck!