What you need:
- disposable umbrella sleeve - I am not sure how widely used these are but all Japanese departments stores and many shops have them, you put your wet brolly in it before entering the shop.
- coloured paper
- things to decorate the wreath with
Once it is full, make the sleeve into a ring and tape the ends together.
Cover the taped ends with a pretty ribbon, remember to make a loop to hang it with.
Stick on your decorations.