I just uploaded Armorysync to my site when I go to Manage Addons I get this:

The install definition file for armorysync did not contain a correct installation class

Please help

I think you tried to install version 253 which is for roster 1.7.3
Get the 2.6 beta for roster 2.0 beta and it should work

No, he's got an earlier 2.0 beta, from before the install class name change. He needs to update to latest.

There are separate error messages for no install class file found and the file does not hold a valid install class.