Help me understand picking up stitches

i am starting a tote bag. after making the base of the bag in garter stitch, it gives instructions of picking up stitches around the base? i was unable to open the link sent to me last night to see how this is done.
also, how do i “slip stitches” on the corners of the base?

Check out the excellent video on this site. Basically, you’re slipping your needle through the edge stitches, looping yarn around it and pulling it through to create live stitches to work, where there were none before.

Slipping the stitches on the corner just means to insert your right needle into the stitch (as if to knit if you’re knitting and as if to purl if you’re purling), and just move it onto the right needle without knitting (or purling) it–literally just slipping it from one needle to the other.

do i need to bind off 1st anfd then start the pick up part of the pattern? this is only the 2nd pattern i have tried without taking a class

No, don’t bind off any sts, you want to leave the ones you’ve been working on, on the needle and pick up the others.