The way I usually do it (see video) you don’t actually pick up anything but your working yarn between existing stitches. What do I pick up?
You pick up your working yarn. But do it as if you were purling. The usual way of doing it as in the video, is as if you were knitting.
Am I working right to left or left to right?
Is the raw edge of the fabric towards me or away from me?
Is the right (public) side on top or bottom?
Do I put the needle between stitches and pick up a bar and purl that?
Or do I put the needle through two as in the video?
Hmmmm, that’s actually 5 more questions…
R to L or L to right depends how you do it. If it’s as in the video, it’s right to left. The edge is on top, the RS facing you. Put the needle through the st and purl it. In the video the needle isn’t actually through 2 sts, it’s through both strands of the BO edge, the chain.