Beginner Pattern Help with Mittens

How-to Questions
1

Hi!

I was moving on to my next project which revolved around knitting mittens. I saw this cute pattern online and was wondering if I could get a breakdown on how I’m supposed to do this:

Do I need 3 or 4 double pointed needles?
I have some yarn from a sweater I made before. Does it matter what kind of yarn it is?
What does it mean by double strand cast on?

2

Cute mittens.
You can either use 3 or 4 dpns to hold the sts plus one more needle to use a your working needle. The gauge for the mittens is 16sts/4inches so something that knits close to that is best. For the pattern as given, they use a yarn the knits at 21sts/4 inches but use two strands of that yarn held together so that they get 16sts/4inches.