Your bbPress MU comes with two default theme installed (Kakumei and Kakumei blue).
To extend available themes you’ll need to install extra themes on your site.
bbPress themes can be downloaded from bbPress Showcase
Installing New Themes
1. Download the new theme(s)
2. Unzip the file to extract all files into a folder on your hard drive
3. Launch FileZilla
4. Enter your domain name, your username and password. NOTE: these are the same username and password that you use to log into your cPanel.
5. Click Quickconnect
6. Locate and open up the folder on your computer that contains the new theme(s).