You should get your own host so you can add plugins and a theme!
How can I get my own host and add those things?
I don't understand. Can someone help me?
Maybe you could explain what but you don't understand?? We could be explaining it all day otherwise
How do I get my own host? I download that then what?
You sign up to a host, you'll probably need your own domain, and you'll get a place to upload the MyBB files. You then install MyBB, import your backup from your current forum, if you can get it, and then you're good to go.
Let me do that for you.
For a free hosting.
http://lmgtfy.com/?q=free+hosting
For a domain.
http://lmgtfy.com/?q=free+domain
If you can understand english then explore those sites and you will get your knowledge better about this easily.
Basicly you can get free hostings like yourdomain.t35.com or something.
And if you want you could put free domains like yoursite.tk or yoursite.co.cc
Or you could just buy a domain from godaddy.com
Or domain and hosting from Bluehost.
Well there are many more sites.