Foreskin restoration (FR as they call it) involved slowly stretching the shaft skin over the head until you have enough to remain covered. There are several methods, much like PE. Using adhesive tape and elastic bands for traction is the most common. Some guys use weights taped to the skin. Others use mechanical devices that gently grasp the skin and then use wights or elastic for the traction.
It takes a long time. On average about three years to get "nice" coverage when flaccid. To be fully covered when erect can take as long as five years of fairly constant work. A book has been around for many years, The Joy of Uncircumcising, and there are a number of good web sites (although the sites come and go as guys make their goals). Do an Internet search on the term and you’ll find lots of information. Here ’s one of the "official" web sites.