Using 2 separate balls of yarn

I’m making a cowl neck poncho. I’ve started on the front and it then says to cast on 76 stitches on a separate needle using a separate ball of yarn. It then says to purl the original 26 stitches then purl 76 on spare needle- 102 St’s. Does this mean that I join the two, if so how do I use 2 separate balls of yarn?
I’m new to knitting, so very confused!
Thanks in advance.

You are probably knitting both sides of the neck opening. You need two separate balls on separate needles because of the hole. At some point you will drop a ball.
P26, your head, p76.

Thank you.