You can get free hosts like MG1 gave you, which give you some limitations, like no custom themes without permission, no modifications, forces Ads you won't earn as 'owner' of the Forums, etc.
For a small amount of money per year, you'll get rid of all of these limitations, a very small amount of webmaster skills is required, but at least you'll really be the Forum owner, without limits*, without worries, free domain name included without the "yourforum.omglookatthisfreeforumdeal.com", no Ads (unless you put your own Ads), and you can install any Forum software you wish.
I can, however, help you on it, but it's your choice if you want to put down like 5 Euro's per year or not, and I'll not force you into it.
* The only limit you'll have, is disk space, but Forums never take up that much data.
In the Admin Panel.
Login with your Admin account, you've created while installing, and look around in the Admin Panel first.
When that's done, you'll understand by yourself.
If not, then tell us what software you're using (most of the time, it's found in the footer), what version (also in the footer), then I'll be able to look after it.
Footer is the text at the very bottom of the page, usually where the Copyright info can be found.