I'm not sure what you want to do here, and since I couldnt afford GMS2 all I know about GM is the 8.0 version of GM Classic, so take this with a grain of salt.
If what you want is to have footstep sound effects, you should make it so the game checks if the player is moving, then in that if statement use the audio_play_sound line (
https://manual.gamemaker.io/monthly...e/Asset_Management/Audio/audio_play_sound.htm)
I'm sorry I couldn't be more clear, I don't know the rest of your movement code so I don't know how I'd have to inmplement it.