Unless stated otherwisr software for IT2007OS won't work on IT2008OS.
A repository is a listing of available software packages on a website in a format that your Nokia tablet can understand. gronmayer.com/it has a list of repositories that contain software compatible with different versions of ITOS. The most common way to "get" a repository is to click one of those green "click to install" links you see on downloads.maemo.org or other places. Usually that will install the application, the needed repositories and get you any supporting software as well as let you use "Application Manager" to download updates in the future.