Login on SEPM >Right click on group >Then click on update content >Ok
FYI, this action causes the client computer to launch LiveUpdate and get updates from a LiveUpdate server, not from the SEPM. There is no way to force-push contents from the SEPM to the clients. Clients must always request it... yes, even in Push mode.
As Joel said above, just allow clients to get their updates via the heartbeat process. If you want them to get new content as soon as possible after it's available, then keep your clients in Push mode; the SEPM prompts them to check in and it is (or should be) randomized to not cause a bandwidth storm.
sandra