The Steam Link app on your phone should scan for your PC, then provide a four-digit PIN
Enter the PIN into the ‘authorise device’ textbox that pops up on your Steam PC client and hit ‘ok’
After that, your device’s name should show up in the Steam PC client’s remote play window
Wait for your Steam Link app to test the network connection, then hit ‘ok’
Hit the ‘start playing’ button to access your Steam library on your phone
Launch GTA V
And there you go! If you’re having trouble and would like a visual guide to help you through the steps above, check out the embedded video from Android 9 Hacks. We also recommend that you use a controller when playing GTA V on mobile, as the touchscreen controls can be a bit cumbersome.