I need help with Yarn Forward

[buster629]

I am just starting a new project which is mostly in purl. The pattern calls for yf (yarn forward). I understand the yf before I do a knit stitch but then it calls for yf between purl stitches. How do I do a yf? The yarn already is in the front. I had to cast on 45 stitches and then after I do the first two rows of all purl I end up with 42 stitches. I must be doing something wrong with the yf. The pattern is:
p1 p2tog p5 yf (k1 yf p5 p3tog p5 yf) twice k1 yf p5 p2tog p1. PLEASE HELP ME IF YOU CAN!

[Silver]

To YF after a purl, bring the yarn under then back over the needle. :)

[nanettecelina]

Silver is right, bring the yarn forward then back as if you have wrapped it around the needle and back to the front. I had a bit of a problem myself the first time I ran across this in a pattern.

[buster629]

Thank you for the yf reply. I will try it and see how it goes. ;)