I found a great Youtube channel for learning how to arm knit. Simply Maggie has several videos from beginner arm knitting to specific techniques and methods. The audio can be a bit off, but overall, the quality  of the explanation is pretty good. Below are some of the videos and a link to the Youtube channel.

Simply Maggie

Arm Knitting 101


3o Minute Scarf


45 Minute Blanket


Ear Warmer


There are also some videos for specific stitch types for those who want to take on more complicated projects.

Linen Stich


Cable Stitch