How do i creat a fourm a site?

i want to creat a fourm site that i can edit in any way i want. also i want it to just have the name of the site in the url. the problum that i am having is that when i try to find a server to host the site for me i makes me add the name of the site to the url ex.www.(sitename).fourmmotion.com how can i get over this problum. i now it is possible because i have seen sites like that where it just says the name of the site with fourm in the bigning ex.fourm.(site name).com. please help me.