Passage: During the course of a game, players gain XP (experience) by completing actions such as constructing buildings, training units, killing enemies and collecting treasures. Whenever a certain amount of experience points are gained, the player can make use of a shipment from their respective Home City. Shipments slow as the game goes on, since more XP is required with every consecutive shipment. This XP is also added directly to the home city and is collected over multiple games, allowing it to level up over time. Players can gear their cards into three different combinations: "Boom" (economic combinations), "Rush" (military combinations), or "Turtle" (defensive combinations). The first few cards chosen are automatically added to the player's portfolio, where it can be copied onto a deck for use in a game. Later in the game, cards have to be manually chosen because of the limit of cards in one deck. Most cards are available to all civilizations, but some are unique to one. If the Home City being played has more than one deck, the player must select which to use when the first shipment is sent. During a game, players keep this initial deck; this feature encourages players to build decks that are customized for the map being played on, or that counter other civilizations. The decks support twenty cards. As the Home City improves by level, you may gain an extra card slot for the decks for every 10 levels.

Question: Name one action the player is able to do when he gained experience.
make use of a shipment