You do the thing in the fiction; you follow the procedure in the rules. That is true in all roleplaying games, of course, but the nature of moves makes those procedures something you have permission to reference. Instead of being expected to remember some obscure rule on page 348, you are in constant engagement with these individual subsystems.
This is a nice description of PTBA, and how despite their light rules you end up having to follow them strictly why more traditional rpg would let more room for GM interpretation of the rules. because nobody want to stall game to check the exact rule which usually isn't in the section where you expect it.