Elements you need:
Fill vase with foam and cover with moss. Use floral pins to secure moss.
Clip branches and place in foam to desired height.
Use greenery, feathers or shrubs to determine the width. You can clip the ends to make them the right size.
Then place flowers, feathers, wooden fruit, or any type of decoration in arrangement.
It is a good idea to follow the rule of odds. Use flowers, leaves, feathers or whatever item in odd numbers for a more pleasing look. You do not have to follow this rule though.
Then place on a mantle or table. On a mantle remember the rule of symmetry does not always apply. If you have a tall floral arrangement on end, you do not need something in equal height on the opposite end. Feel free to get creative.