Love, love, love these urns. I have had the urns for several years and the fall decor is several years old now too, so I don't have any pictures of the step-by-step directions.
BUT, I will try and tell you how they are done, any questions please contact me.
I change them seasonally. In following posts I will show the seasonal changes to you. To be able to change these easily each season, I have the flowers molded with Plaster of Paris in coffee cans. So make sure whatever urn you want to place the cans in will fit into the urn. These are actually tin coffee cans, so you can tell how old they are and how well the flowers have held up. The flowers are about three foot long and I have them tied together with wire and then place vines weaved in-between them. If after placing the flowers in the urns you want more height just add a block of wood to the bottom of the urn, or whatever you can find. I then fill in the space around the edges to the top with plastic bags and place decorative moss around the top of the urn.