When you read a chart, each square represents one stitch. The front, or right side of the pattern is read left to right and the back is read right to left. Intarsia patterns are best worked back and forth rather than in the round.
You have to be careful when you switch colors or you will get holes. Amy has video of intarsia knitting in the Advanced Techniques secion. For some reason I can't create a link tonight.
is an informative site on intarsia, also.