do you have a 240v line run to your timer ?
if so it's pretty self explantory on your timer you will see terminals that say line or load your 240v line goes on line . tie your 120 v from your gfi's to the terminals marked load . OH if your run a 240v line from your panel you need 2 hots ,a neutrel, and a ground without the nuetrel your fucked . so thats three insulated conducters and a ground . If you have the nuetrel there you would just join the nutrels from your gfi's
to your neutrel from the panel .