Start with an On Key Pressed trigger, or any key is down, depending on your needs. Then as a sub-condition use the system Compare Two Values expression. In the top line enter your 3 keyboard conditions separated by " | " (remove quotation marks). Like:
Keyboard.LastKeyCode = 50 | Keyboard.LastKeyCode = 51 | Keyboard.LastKeyCode = 52
These are the conditions you are "OR" checking for one of them to be TRUE, so the rest of the Compare Two Values should be "= 1 ", where 1 represents TRUE.
I personally use player control variables (booleans) where I set these to true or false at the start of the player control layout, so when I need to check if a control input is made I just check the single variable rather than repeating all of the above code.