The aircraft payload can be controlled using the EFB tablet, which allows you to select a variety of configurations for the air-defence, weapons training and Red Arrows display roles. 

Selecting an aircraft configuration (T1, T1/A or Red Arrows) on the EFB tablet will automatically select an appropriate payload for that configuration.

Due to simulator limitations, any payload changes made via the EFB won’t be reflected on the MSFS fuel window, therefore the total payload and aircraft weights are also shown on the EFB and update in real-time as configuration changes are made.

See page 97 of the manual for more information.