A client can only initiate a backup from their side if they have a "User Backup" defined for a particular policy on the master server.
As for restores, if you go under "Host Properties" on the master server, then go to "Client Attributes", add your client(s) to the server list, and then on the "General" tab, there is an option at the top to allow for client-directed restores.
The restore information is listed on pg. 382 of the Unix admin guide vol.1,a nd pg 386 of the Windows admin guide, vol.1
