Source from: http://www.archeage-store.com/news/game-ArcheAge-33/How-to-Level-Up-Mount-in-ArcheAge-Online-13792
ArcheAge mounts, for players, you can buy or breed mounts. Mounts are very useful when they become adult. You can summon them to fight around the game world.
Similar to your character, a mount has its own name, health bar, stats, experience, level. and so on. For example, the following screenshot is a horse mount.
From the above picture, you can see mount information:
Mount Attributes: Strength, Spirit, Intellect, Stamina, Agility
Mount Stats: Vitality, Energy
Mount experience Points
When you gain a mount, you can give it a name, which will show over its head. If you want to change its name, you just click their health bar and output new name. Actually, as your mount is leveled up, it can do lots thing for you like your character. Additionally, you can feed your mounts to improve their attributes and stats.
If you want the mounts to fight, the first thing you have to do is to upgrade your mounts.
Mount can be upgraded by traveling. You can summon your mount to travel. In process of traveling, the mount can obtain experience points.
Fighting is another way to level mounts up. As it helps your character fight against monsters, your mount can share the experience points you gain in battle.
Finally, there is recommendation that all of mounts can not be leveled up in ArcheAge. Some of mounts, like horses, snow lions and elk, can be used to travel and fight.