To activate one of the seven saved custom profiles, select SHOOTING MENU 3 > SELECT CUSTOM SETTING and chose your desired profile.
The Q button can also save you some time here: tap the Q button to bring up the Quick Menu and then select from C1 to C7 in the setting field in the top left. The shooting settings associated with each profile will display in the Quick Menu so you can get an overview of the definitions for each setting.
The third option to switch between custom profiles quickly is to program the Fn button to serve this purpose. Hold the Fn button until the configuration menu appears and then assign SELECT CUSTOM SETTING.
Which profiles should you save? Only you can answer this ...