The Atari 7800 can have two joystick controllers attached. Use the ARROW KEYS (up, down, left, right) to move, the CONTROL key for button 1 (usually fire), and the ALT/OPTION key for button 2. Pressing I will select, and O will pause.
The controls for the second joystick are R, F, D, G for up, down, left and right, the A key for button 1 and S key for button 2.