Brand new knitter--help w/ changing color

[Stacey]

Hi-I'm attempting to knit my first scarf with colored stripes. I am not sure of the best way to join in the new color, can I just twist the new color around the original and keep knitting? Also, how do you "carry" the colors up the scarf? I have read about it, but I don't understand exactly what it means or how to do it. I really appreciate the help. Thank you.

Stacey