When one of these tokens is on top of an Adventure deck, it reminds you that you must draw an Adventure card next time you resolve an Action of the appropriate type. Then discard the token.
An Adventure token overrules the result of the Adventure die, if it is rolled. Even if you roll the die and get an Adventure result, you only draw one card, not two.
If Friday is resolving the Action (alone or with neutral pawns) and there is an Adventure token, he takes 1 Wound instead of drawing a card. Then discard the token.