Fader select allows you to control the channel faders using the main control Encoder (Located in the bottom right of the Screen section). 

Enter the Setup menu and activate the Fader Select Mode (Located under "Surface and Lights"). 

If you then select your channel and press home, tap the fader on the display and a Yellow highlight will appear around it. You can then use the Encoder to adjust the fader. This is great for really fine tuning the level of the fader.