If you are talking about the drivers, you would steer with handle bars like on a bicycle, move handle to the left to turn left, to the right to turn right.
These are only driver units, they go forward and reverse with the pedals, down in front to go forward, down in back to reverse.
They connect with a ball hitch like a truck and trailer so there is a pivot point there so you can turn the striper or whatever else you want to connect.
You can connect a billygoat blower, just put some handle bars on it so you can steer. I tried putting the hitch into the space in a hand truck, tilted the hand truck back towards me and since it was supporting the front of the driver (hitch), I drove it around and steered with the hand truck handle.
This uses hydraulic pump motors like zero turn mowers to go forward and backward and they are strong.
There are a lot of youtube videos on parking lot striping if you want to see them in action, after a little bit of practice you are using them like second nature.