I now know how to make arm-holes in a sweater for a dog, but how would I make little sleeves? Thanks in advance to anyone who can help! bear in mind I’m very new at knitting so nothing too complicated please! 
Easiest would be to pick up stitches around the arm/leg holes and knit until they’re the length you want.
how would I go about picking up stitches? sorry for being so thick but I really am quite hopeless at learning more difficult knitting things! thanks!
There’s a video in the knitting tips section on it. Go way down to the bottom http://www.knittinghelp.com/videos/knitting-tips