Packages that deliver game server commands should include the username_id of the user, dependent on your store type.
You can get the username_id after creating the basket if you provide the player's username at the time of creation. See Creating a Basket for specific details on Game Servers.
Custom Data
You can also provide custom data when adding packages which can be referenced by the seller as part of the transaction.
Specifying the Package's Game Server
If a package with a Game Server Command has the configuration option:
Allow customers to select the game server they want to receive this package on.
You can specify the target game server in the request by including server_id in your package's variable_data:
A list of your server_ids can be found in your Tebex Control Panel by clicking Edit beside your relevant game server. The server ID is the number at the end of the URL when editing the game server.