From b2evolution manual
This manual page is outdated. NEW PAGE: Installing Skins in b2evolution v5+.
- Download a skin from the Skin Directory.
- Unzip the file. If you're not sure how to do this, try double clicking the file that you downloaded. The end result should be a folder filled with files (e.g., _main.php).
- Connect to the web space where b2evolution is installed via ftp and upload the folder to the skins folder in your b2evolution install.
- Go to "Global Settings" > "Skin install" > "Install new" (this step is needed in b2evo 2.0+)
- Go to "Blog Settings", choose your blog and change the skin.