That sounds more complicated that it is. I don't know how much detailed information you want, but here's some basics.
To make the pattern come out correctly when you increase or decrease it's size you work with multiples of a number. In this case moss/seed stitch require a multiple of 2 because you knit 1, purl 1 to do it. The plus one is only to make it come out right and you only add it once no matter how many you cast on. For a multiple of 2 plus 1 you'd end up with an odd number.
4 + 1= 5 stitches
6 + 1= 7 stitches, etc..
The edge stitches are often there for seaming.
You alternate what stitch you start with on each row because in order for seed/moss stitch to come out you have to knit the knits and purl the purls. (each stitch has two sides, one a knit and one a purl..I'll add picture in case you don't know what they look like) So your rows would look like this assuming the last stitch is knit on both sides. That I'm not sure of as it doesn't say on your post.
Row 1 - k1, (k1, p1 across to last two stitches), k1, k1
Row 2 - k1, (p1, k1 across to last two stitches), p1, k1
It doesn't matter how you knit really. There are lots of ways to do it.