Two I believe. Look further on in the directions for verification of this. If in the finishing or assembling or where ever it tells you to sew the 2 chassis pieces together somehow you have the assurance that you need two.
Many folks when they learn to knit, learn a little different method than is shown in most beginner books for how to do the knit and purl. Sometimes people learn to wrap the purl in the opposite direction and that requires the knit stitches all to be worked (when knitting flat) through the back loop. But if you don't realize you should be knitting through the back loop you will twist all the stitches and that looks a bit differently. You can either knit through the back loop, or wrap the purls the other way to correct the problem.
There may be other little things that happen that could cause odd looking stitches. If we could see a sample of you knitting, close up and clear we might be able to help. You may not be able to post a picture yet, but if you make a few posts somewhere you will be able to. Commenting on other folk's knitting in the "What'cha Knittin" forum would be a way to get a few posts.
Welcome to KnittingHelp!