Metadata is a set of unique data (in this case, a name, description, and image) that will later be displayed on your assets. You can set metadata for any assets you've created via the "Assets" panel..
Click "Edit" on the asset you wish to set metadata for. This will bring up the "Asset Details" page. From here, you can input (or edit) the asset name, description, and upload an image (recommended 1000x1000 px).
Note: Metadata is hosted by Enjin. You can change an asset's name, description, or image at any time.
Once complete, save your changes. A notification will be sent to the wallet linked to your project. Accept the request and enter your password to confirm.
The transaction will then broadcast on the blockchain. Once the transaction has confirmed, you will be able to see your asset's unique metadata in the Enjin Wallet and on EnjinX.