You will want to create layers within the container for drainage, first pea gravel, then larger rocks, and finally potting soil.
Remove all plants from their containers, taking care to not damage the root systems of the plants.
Place large interesting found objects first; keeping in mind spaces for your plants.
Place plants in groupings and scattered through the container for a natural woodland feeling.
Lastly add extra treasures like moss, sea glass, rocks, and any other fun item that makes your garden sparkle.