I would say you inc on the 4th row and not the first one unless it says something like "increase in the first (or next) and then every following 4th row".
I like to use a front/back increase in this kind of case. You can make a fb inc either k or p as needed.
So if you have KKPPKKPPKKPPKK you will want to add the next stitch at each end as a P. Until you do the next inc you will not have 2 there but that will look okay. So in this case you work into the first K st by purling into the front of it, then knitting into the back of it. That adds a P before the first K and retains the existing knit that was the first stitch. At the end of the row you have 2 knits so you want a purl next, so knit into the front of the st then purl it tbl.
Now you have PKKPPKKPPKKPPKKP.
On your next inc row you need another purl at each end so purl into the front and back of each end stitch. P in back tbl.
Then you will have PPKKPPKKPPKKPPKKPP
On your next inc row you will want to add a knit st to each end so begin by doing a k in front and a purl in back tbl of the first purl. At the end you need a knit so purl into the purl in front then knit it in back.
Now you have KPPKKPPKKPPKKPPKKPPK
Now you need another knit on each end so into the beg and ending knit sts, kfb.
That will give you KKPPKKPPKKPPKKPPKKPPKK
I suppose that the increase video shows how to do a kfb, I'm not sure if it shows a kfpb, or a pfkb, or even a pfpb, but they can all be done.
I hope that makes sense.