To call an elevator, just 'push up on elevator' or 'push down on elevator' to indicate which direction you want to go. When the doors open, walk in.
The elevator is exceedingly simple to use. inside, just 'push <num>' to select a floor, and 'out' to leave the elevator when the doors open. You can also 'push open' and 'push close' to manipulate the doors if you like.