How to install a theme from Cydia

To installa a theme from Cydia, you first have to download and install winterboard.

After that, simply download a theme from cydia and select it from winterboard list

How to install a theme with SSH

To install a theme with SSH, fist of all you have to install sbsettings and open SSH from cydia. You also have to install a SSH client on your pc, like winscp for windows

After you are connected via ssh with your iphone, simply go to "Library" folder, and copy your theme into "Themes" folder.

Once you have done this, simply select  your theme in Winterboard