This detailed 9 step guide will teach you how to hem sweatpants with elastic at the leg opening. This guide is easy to follow and anyone can do it.
The process requires a very basic knowledge of sewing, and can be done either with a sewing needle or a sewing machine, with the steps displaying how to use either. You also need to know how to use a seam ripper.
Lastly, like most guides hemming a pant leg, this process is not reversible, so make sure you measure correctly.