Use this guide for EASY install repositories and addons for XBMC
UPDATE : new adress, dont use http://hub.gosub.dk use http://fusion.xbmchub.com/ instead
1. Open XBMC – Goto ‘System’ then ‘File Manager’
2. Click ‘add source’
3. Type http://hub.gosub.dk into the <None> field
4. Enter a name for the source eg gosub and click OK
You have now completed all the steps needed to add the share. This will only need to be done once on each XBMC device.
You can now access the newly added share by going to System and selecting Addons from the left.
Then click ‘Install from zip file’
Select ‘gosub’ or whatever you called the share
Then click to install any addonrepo from the list