First, equip the Geiger metre (in real life it’s not the proper tool to use to measure absorption but the devs have tried to make this fun more than bothersome realistic).
Wash yourself in water -submerge yourself to shoulders or just swim around.
You obviously don’t want any contaminated items near you, thus Treat everything you took into the hot zone as contaminated and either discard it or wash it.
Any contaminated clothes that you want to keep need to be washed with soap and water.
Drink heaps of water -Keep doing so until your character needs to urinate.
Urination is the best way to reduce internal radiation and washing yourself is best for external.
Tablets were a waste unless you go above 2 seiverts (note this is not %, but an actual value).