I have a Pfaff 7570 and it looks the same as this. When you open up the cover on top, mine shows arrows as to what path to follow. Put the thread around the square box above the L shaped hole, bring it down through the slot on the left side, then up through the slot on the right side, around the hook, then back down the slot on the right. There is a slot near the needle, put through there then thread the needle. Hope this helps.
Ahh! Thank you. I was trying to do the slot on the right side first instead of the left side. Wow! I nearly threw the machine at the wall last night, I was sewwww frustrated!
I am not sure if the link will work or if it will help you, but it is worth a shot. The video is "Threading a Pfaff Sewing Machine Select.mov"
It is not the exact machine but it helped others with different models. Good luck!
Youtube links never work here...put the name (I put it inside quotes) in the youtube search box