I put them together by laying the machine flat on it's back, putting the switch buttons in their proper positions and then with one hand.. holding the front cover up and with two fingers pinching the buttons together, so they stay in the same place when you pop the switch cover into place.
Once you're holding the switch cover and buttons properly, place one hand behind the switches on the machine and lay the cover into place from the bottom up. Hope this helps, takes a bit of practice.