my english is not the best, i hope you will understand
First setup an idle and walk/run animation. you can do this when you double click on your player and you will see a screen with default, here you can add the animations.
add the platform behavior to your player or - playerbox (not necessary)
Go to your event sheet and setup your movement, like key 'd' is down simulate control to the left, and add action not mirrored, for the left you do the same but than set not mirrored to mirrored.
ok, now thats done setup a trigger in your eventsheet
'player - on moved'
ok next you do is
right click on it and add a sub event
player - is on floor, right you see ''add action'' now add your player and ''set animation'' - you can do this - " - and you will see the animations that you setup, like idle and walk, choose walk.
your guy need to rest, when he's not moving,
go to the event sheet and select your player, add '' on stopped'' trigger
right click on it and add an sub event, player is on floor, add action on the right and do this again " select idle.