Bring the thread up through the fabric. Hold the thread to the left and make a loop, reinsert the needle at the starting position, bring it up again a small length away passing it over the loop you made earlier. (Photo 1)
Pull the thread through. Be careful not to pull too tight at this point, you just want to create the loop. (Photo 2)
Repeat the loop, and reinsert the needle where you came up before. (inside the previous chain stitch)
Chain stitch can be used as a filler for an area of your design if it is worked in rows.