Help Novice Knitter

[LMCGA]

I am knitting a scarf which calls for a "flat knot". The instructions for this are as follows:

"This knot is worked over 3 stitches: P3tog, yo, purl the same 3 stitches together again."

I am clueless about how to purl the same stitches together a second time. Do I keep them on the left hand needle? Do I purl just the single stitch or do I reach down and purl the 3 stitches individually again? And, if so, how on earth is this done?

I have tried this every way that I find possible and the results are a big mound of moosh.

Any response would be soooooooooo greatly appreciated.