Here is a video showing me picking up and knitting stitches along the edge of my knitting. I've shown both selvedge and bound off edge as the pick up ratio will be different. Typically in knitting you will 'pick up and knit' as shown in this video but if you just want to 'pick up' stitches then you only do the first step of putting your needle through the edge of your knitting.
You can learn a bit more about about the ratio for picking up stitches in this video along with more demonstrations on picking up and knitting stitches.
