By following the waypoints and objectives you get led to lowering the radiation.

This guide will only point you towards actions and contains no spoilers.

But the 6 points of lowering the radiation is (In any order):

Cut the ship open with huge cannon and go inside.
Fix the mayo launch shuttle.
Open the bio module and do objectives inside
Create Ceder Spacesuit
Make Beef pellets and fuel a frozen ship
In the round electric ball building, go look at a blueprint/paper that tells you to turn on lower radiation in settings......

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