Have you ever been repairing something, and just don't have a "helping hands" or another person or way of supporting that project you're doing? Or that roll of solder is just too big to hold onto while you're working? Try this way and see how it works!
The easiest way to explain it is with pictures, and a minimal amount of wording. Simply put.. pull off a strip of solder from your roll, and cut it, or sharply pull it until it breaks free (i prefer the latter).
Take the strand and wrap it around your index finger of your non-soldering hand similar to the image you see. Leave a "tail" long enough so that you don't burn the tip of your finger as you solder (i'm not responsible for you "tinning" or burning your fingers... fingers when burnt hurt quite a bit.. take my word on that)
As you use the solder, undoubtedly you will, unravel it around your finger similar to how you would with a roll, remembering to leave a decent-length "tail".
Your soldering style will influence how you hold the solder and what length of a "tail" will benefit you the best. The images I've provided serve as a reference point only.