First set up your controller. The upper left where you see the which controller are you using, click on this to bring up the standard studio one picture of your controller buttons, faders whatever, right click a button to assign parameter scroll to transport set buttons, stop, start , if you hover over the transport controls they will tell you what they are(their proper names), then just choose and assign on your picture of your controller, midi learn kinda thing. If your midi keyboard is not on the list of studio one keyboards (where you go to set up midi), mine is not then choose the closest one and that should work, it does for me
