Why two you ask ? Well if the two motors, which are connected to wheels turn in the same direction, then the mower goes forward. If they turn at different speeds the mower turns.
This is best understood by watching this video
The motors of course need to be controlled , for this you need a motor speed controller. These can be purchased from a number of sources ( choose wisely) .
Then just plug the speed controller into your RC receiver an hey presto the wheels are being controlled through your RC handset. That is if you've remembered to plug in the battery.
Wheels, batteries and electronic thingamies, need something to sit on and some way of attaching to a mower. This is the really clever bit and you will be amazed at what you see on the video.