I don't see why he'd need a tutorial for such basic movement.
It's very simple really. You just need to use keyboard_check to check the keys and then move the character in that direction along the X and Y coords.
Using keyboard_check:
if keyboard_check(vk_up)//(ord("W') is used for WASD controls here
{ target_y+=16;}
if target_y>y {y+=4;}
That simple code will move the character northwards. From there you can define things to better suit your game, such as making it so the player moves on an invisible grid (which can be done by adding a check to see if target_y=y and target_x=x) or checking to make sure other keys aren't being pressed. It is really simple though, just take it and go experiment with it and if you run into any problems with it we'll be here to answer any questions you might have.