Confused by this mittens pattern!

Hi! I’m trying to knit these mittens:

And I have to say, I have been confused by almost every step! I am particularly confused about adding in the thumb gusset. I really don’t know how to add the thumb gusset steps into the “Twisted slip stitch pattern” part. Any advice there? How does the thumb gusset pattern affect the twisted slip stitch pattern?
Then, within the thumb gusset instructions, it says to repeat steps 2 and 3. But how can I repeat step 3? Step 3 adds new stitches, so it doesn’t fit the number of stitches the next time around. What am I missing?
Then, after that, it says “knit even to bottom of thumb” and I don’t know what that means. Where is the bottom of the thumb?

And that’s as far as I’ve gotten!
Sorry for all of these questions! I hope there is just something I’m not getting because everyone in the comments of this pattern says it was great and easy!

Thank you so much for your help!

When you increase stitches you’ll have to shift the main pattern st over so the new sts can be part of the pattern. So instead of starting with stitch 1 on the next round, you’ll need to begin with the stitch before it.