Welcome Yvonne!
Glad you like the site!
Yes, you can just start using ML at any time, although you'll have to switch to a longer cable to do it. (With the interchangable needles this is easy: just use your cable joiner, and slide the work onto the new cable!) Then, to begin knitting, pull the cable out from between two stitches, on the opposite side of the last stitch you knitted. Then slide the knitting up, as in the video, to begin knitting.
That's great, I hope you love it! Let us know!
Amy