Baby/doll sweater

So, my mum completed her scarf much faster than I expected(4 days!).
Now she’s knitting a doll sweater based on this pattern:
and of course I have to help her.
My problem is how do you cast on stitches on a piece your working on(here to form sleeves)?
It’s quite urgent, cause she will be at this point tomorrow if she continues at this speed!

Check out Amy’s Knitting-on or cable-cast-on videos. They show how to cast on with only one piece of yarn (as opposed to the double-cast on where you use the long tail to do the cast-on.

Good luck!

Thanks :cheering:
How could I miss that one? :doh: