If you are knitting flat (not in the round) garter stitch is just knitting every row. Both sides look the same.
Seed stitch is alternating 1 purl and 1 knit on the same row. When you turn your work you will be doing the same thing, but you'll be knitting into the purl stitches and purling into the knitting stitches.
There are videos for knitting and purling which is what all knitting is made of.
Here's some hints I share with new knitters... Learn what your stitches look like and how to identify them when they are on the needle
. This will make your knitting life from here on out so much easier. Here's a little knit sample I made to show what they look like. When you flip this over you'll see that the knits now are purls. Each stitch has two sides one is a purl and one is a knit. That's why this is important.