Hi robert,
First you'll need to complete the tutorial at the very beginning of the game. It takes a little while, and uses the keyboard. Onscreen instructions will appear and you have to follow them exactly in order to move the tutorial forward to the end.
At the end of the tutorial, you'll be able to choose which mode you prefer to play in. You can do this by pressing R on your keyboard several times to switch through the available modes.
acebook
witter
