The cover is made in joined rounds of single crochet. Each round is completed with a slip stitch to the first stitch of the round (do not count the slip stitch used to join each round as a stitch). You may wish to use stitch markers to mark the beginning of each row to keep track more easily.

The first stitch of each round is made in the very first stitch of the previous round (the same stitch in which the join/slip stitch and ch-1 was made).
Close the magic ring and weave in the loose end at the beginning since it gets very narrow as you work and it will be difficult to weave in at the end.

You can always add or delete rounds to make the cover longer or shorter to fit your wreath hanger.