See my simple step-by-step tissue paper puff tutorial here. (For these wreaths I cut the tissue to 1/8 the size of the giant puffs, which used full-size sheets.)
Next, cut a large circle out of craft paper to the size you'd like your wreath. Bunch the tissue paper puffs tightly together and glue onto the paper.
Once it dries, hang the wreath and enjoy!
Merry Christmas and happy crafting!