How to upgrade NFT?

Click on the button with the green arrow up on the character image:

A confirmation window will appear. The cost of raising the level is affected by the current level of the character and the number of team defeats. You can speed up the level increase by spending $TON, more information can be found in the sections "Raising the level" and "Penalties for defeat" of the article:

The price includes a service commission of 6%. After deducting the commission, the $TON invested by the participants is collected in the treasury. After the victory of your Faction, the invested funds will be returned and a reward will be awarded.