Start cutting apart the lemon branches in 6-8 inch sections.
Arrange the lemon branches around the wreath.
Take each lemon branch and add hot glue to the end, then stick it into the wreath. Continue with the other branches.
Cut apart the white flowers and hot glue them into the wreath at varying intervals between the lemons.
Cut sections of faux greenery to fill in the wreath as desired.
Hang the wreath and add or adjust the florals as you like.
Notes
You could use floral wire to attach your pieces to the wreath. This would make it less permanent so that you could use the pieces and the wreath form again in the future. However, I think using a hot glue gun is faster and easier.