Help joining a 2nd ball

I am very new to knitting! I’ve only been taking lessons for 3 weeks now. I can’t get to my teacher today and have to join a new ball of yarn so that I’m working 2 balls at the same time (making a v neck sweater). Can anyone tell me how to add the second ball? Thanks so much!

Just start knitting with the second ball. You can weave in the end later.