Hi Dodyan. If you find that part too confusing, it's perfectly acceptable, and common practice, to pick up just one stitch in the middle of that crux of the thumb area, wherever you like. You will have a gap on either side, which can be later closed up with the end yarn using a yarn needle, as I also demonstrate in the video. Picking up three stitches over the gap, and decreasing two of them on the next round, is an option that I demonstrate in the video, but hardly a requirement.
And yes, I believe I begin the picking up stitches with the fourth needle, which then knits the stitches off the following needle, freeing up the fourth needle once again, which is necessary to continue working.
I'm glad you're enjoying the pattern. Good luck with that part, I hope this is clear enough for you.