Started here: Knitting 101: Learn How to Knit

Then tried this: How to Knit a Hat

Magic Loop Technique: How To Knit in the Round Using a Single Long Circular Needle

Knitting Help – 3 Ways to Join In-the-Round

1. [Easiest] Slide first stitch off left needle (let it hang), slip a stitch from the right needle to the left, pick up the hanging stitch with the right needle. This swaps the two stitches. Place stitch marker before continuing.
2. Cast on one extra stitch, transfer one stitch from the left needle to the right, and bind off, transfer that stitch to the left needle. Place stitch marker and transfer a stitch from the left needle to the right. [Might make a smoother edge.]
3. Don’t join and weave in the tail to hide the “jog”.

The Mattress Stitch: Sewing for Knitters

Seaming 101

Slipping stitches