Question: how to connect wireless keyboard to retropie?
Answer: Connect your Bluetooth adapter. ... 
Connect a wired USB controller (or keyboard) ... 
Update your controller's firmware. ... 
Verify RetroPie version. ... 
Open RetroPie Setup. ... 
Open Bluetooth device config. ... 
Register a new Bluetooth device to pair the controller with your Pi. ... 
Tell Emulation Station to recognize the controller on boot.