just press play I guess. I recommend turbo mode (shift click the green flag) and fiddle with the turn speed slider for interesting results. Ants will try to follow the trails laid down by other ants, the turn speed is how fast they will turn towards these trails. setting the turn speed to negative makes them turn away from the trails.
So recently I watched some videos about simulating ants and ant pheromone trails behaviours. So I decided to try recreating it. It kinda works I guess but they end up following their own trails and it would work a lot better with more ants. The number in the top right is how many ticks have passed.