First select the "Unit" tab. Depending on which Commander you have previously selected, you will now see the units of the corresponding faction divided into different tier levels. In this way you can also look at the appearance of the higher units. In addition to the commander skills, there are also the unit skills, which are also shown. The green sign at the top right of each individual unit is the unit experience you have already gained.

If you now select a unit via the selection below or via the "Unit" display, the equipment window will open. In order to unlock the unit of the next tier, you need certain equipment upgrades. Some of these are really required, others are optional. But I generally recommend the optional equipment can only really be bought from Tier VII (7). Until then, it's usually of little use.

To unlock you need unit experience (green), which you only get by playing matches.

The otherwise greyed-out boxes are so-called "Unit XP Tokens" with which you level faster, which can only be obtained through later quests. (See 6.)

In the "Stats" tab you can view your unit statistics in great detail. If you hover over individual statistics, shows exactly what it is. The statistic is generally something that primarily for the high tier, experienced people, as well as cavalry players is important.

The "Information" tab is nice if you also want to learn a bit about the history of the unit. Otherwise not relevant to the game.