All you need to do is secure the burlap in the embroidery hoop and cut a 12"+ strand of yarn. If your kiddo is older, they can thread the needle, or you can thread it for your tot. Tie a knot at the other end and let them get to work making whatever sort of design they'd like.
Extension Activities for Older Children:
offer large buttons to sew onto the burlap
use index cards with simple shapes for them to re-create on the burlap