It's true that the best way to get software on your WHS machine which is meant to be headless (no monitor) is to install WHS addins. A great place to find addins is whsplus.com
This is because they have be written to be installed easily, as mentioned, follow awraynor instructions.
Windows Home Server is based on Windows Server 2003, therefore any program written for WS2003 can be installed on WHS, you would have to do a Remote Desktop Connection (RDC) to see the WHS desktop and go from there. The biggest warning I can give you here in to be careful installing any software that might make changes to the servers network card. If you disable it or put up a firewall that blocks it then you have a problem if you don't have a monitor.
I googled memopal and if I'm correct it is a Online Backup solution. Looks like they don't have a addin. I would suggest KeepVault or Cloudberry to keep things simple, you can find them at http://www.whsplus.com/