It's asking hero level 6 how to update her?

To increase the level of heroes you need to go to the hero menu. Tap on the hero that you need to level up. Then in the individual heroes screen you will see their current level shown in the top left. Tap on that level icon and you will have the option to use any Exp bonus items that you have received to increase the heroes level.

You can also activate and upgrade the heroes skills. Development heroes have a skill that grants them Exp when they performs actions. Combat heroes gain Exp when they fight.