are you actually starting to plane along before you try getting into the straps? it might just be lack of speed
the more speed you've got, the less hull is in the water and the further back the pivot point (red dot) gets, and the easier it is to work your way back down the tail of the board without it rounding up into the wind. as the board loses speed and drops off the plane, most folk need to quickly move their feet forward again
Generally most people learn using the
front foot first approach (but not all)
most seem to find it easiest to head across wind or slightly down wind on their first attempts
once you get the front foot in, concentrate on keeping the board flat (bottom pic). First attempts often result in too much pressure on the heels and therefore rounding up into the wind. to avoid this it may require you to conciously put pressure on your toes, pulling up on the strap with the arch of your foot, and lift your heels a bit. This will keep you going in a straight line
once you get both feet in and are maintining speed, you can tilt the board (A & B bottom pic) and make it turn left or right like a surfboard, but you gotta be planing to do it
here are a couple of really bad pictures that might help