HP scarves

[kristilynn5 <kristilynn5@yahoo.com>]

I am trying my hand at knitting, and I have a question.  I am 
knitting a scarf with circular needles so it will make a tube, but I 
am confused about thesize of needle I should use and how to switch 
colors.  I started one with straight needles, but Idon't think I 
switched colors correctly.  Are their any avid knitters out there who 
could help me? 

Thanks oh so much,
Kristi