need help with mittens

So im knitting a pair of mittens and was wondering if i have to do this or not? https://www.youtube.com/watch?v=jQ-LGsNil1g Timestamp 5.33-5-47

Welcome to KnittingHelp!
Is it the particular cast on that’s used? You can substitute your favorite stretchy cast on here.
Or are you asking about something else in the video?

Thank you
I mean the part where she threads the yarn through the 4 stitches and I think she sews it together so the thumb part is created? Im new knitter sorry

So at about 5:30 min into the video. If you want the top of the thumb closed, yes, that’s the way to do it. If you want an open thumb, then knit fewer rows on the thumb and bind off the sts.
For the finishing, the thumb is seamed up and that’ll work either open or closed off.

We’re always happy to have new knitters ask questions here so don’t hesitate.