Assuming the film is loaded properly and the film retainer spool knobs are locked on both sides, here is what I do:
1) Pull the film straight up so you have enough to fit into the empty spool.
2) Use the film advance lever to position an empty slot on the spool to face up and insert the film leader into the spool.
3) Make sure the film is aligned with the spool sides and gently press down the film while you advance the film wind lever slowly to the end position.
4) Keep guiding the film as you repeat the above until arrows on the film hit the 120 mark on the top of the camera.
5) Gently close the camera back and make sure it is locked.
6) Keep advancing the film until the shutter is cocked and the film counter hits 1.
Here is a link to film loading in the 67 manual (page 15 to 19, which explains it better than the 6x7 manual:
Pentax 67 Manual
Phil.