Shards need to be redeemed for complete items before they can be used or sold to other players in the Item Marketplace. The more shards you redeem, the rarer and more valuable the resulting item will be. 

You can use the shards that you've earned in-game by:

1. Select the "Inventory" option from the menu. It's in the top right area and looks like a backpack.

2.  After accessing the Inventory dashboard, select the desired shard and click on the "Use" option. 

3. Combine shards to create items to use in the game.