Hello Lika. How are you?
"Up and at'em!" Means to (a) get up, as in get out of bed and (b) "at'em" means Get at them, which means to do the things which are on the daily schdule.
Particularly, this is an expression one might hear in a Military Barracks when the troops are awakened by a Drill Instructor or other Non-Commissioned Officer.
. "Up and at'em" ...should also be your approach to learning English! ha ha .