Then you will have to do your compulsory action after you have setup your camp. See page 4 of the rules:
On your turn, you must perform an Action.
In addition to this compulsory Action, you can set up Camp.
You can also Recruit a new Character.
Those two phases are optional: each of them can be done any time during the player’s
turn, before or after the compulsory Action, but never simultaneously.