At the beginning, click the answer on the menu you want selected. If your playing single player, it's space on pc and tap on mobile. If your doing multiplayer on pc, it's a or left arrow for red and d or left arrow. If your doing multiplayer on mobile, tap on your side of the screen.
I got some of the general bot code from a tug-o-war by @unknownthingamabob (https://scratch.mit.edu/projects/996146).