1) You'll be "picking up stitches and crocheting" to make those double crochet stitches.
2) Bearing that in mind, when the instructions direct you to "insert hook in next stitch," that's when you're picking up the new stitch via the insertion of the hook.
3) This site
has both written instructions and a video of dc 2 tog.
My search string was
dc 2 sts tog video
so if the video I've linked to doesn't help you, just do a second search and find other videos. There were others on page 1, but my computer decided not to let me see the search again. (In fact, my computer went into such a bad "hang/freeze" that I had to quit out of my browser and re-open, losing my New Posts.... grrr.)
Hope this helps!