I found that jfw0371 had a post that solved my problem (and I feel rather stupid). I needed to turn on the radio (the ATC window will open if the radios are off, but you can't use them). I got to the radio stack via shift+2 (the radio button is the tower icon). Clearly I need to think more like a pilot and less like a computer gamer. Also, manuals and checklists. Oh well, live and learn.