1.
Decide roughly where you're going to pick up your stitches along the edge of your work. You're looking for points where you can insert your needle under two bars to then pick up a stitch. Try to space these evenly to avoid large holes. However, holes can easily be fixed when you weave in your ends, so don't worry too much about being precise.
2.
Insert your needle under two bars, loop your yarn around your needle as you would for a knit stitch, remembering to leave a tail to weave in when first joining the yarn.
3.
Bring your needle back through to the front of the fabric, with the loop still wrapped around it.
4.
Repeat steps two and three for each stitch you need to pick up.