The readme.html file in the \samples\com.microsoft.tfs.sdk.samples.checkinpolicy folder should provide additional information, let me know what additional information we should add to the guidance there and I'll see about getting it added.
Basically, check in policies are deployed as regular Eclipse plug-ins making use of the com.microsoft.tfs.checkinpolicies.checkinPolicy extension point. Once you have created your Eclipse plug-in you can create a standard Eclipse update site project
and then make your check-in policy plug-in available as part of an Eclipse update site inside your organization. For a tutorial on creating an Update site in Eclipse see