Upgrade Hero from Dungeon and HBM (Here Be Monsters)
When sweeping in either one you are notified if a hero reaches a max for a level or can be evolved. (Pic.1)
My suggestion is:
When you click on the hero's icon being notified about (Pic.2), you get that hero's Altar page (Pic. 3) from where you can then upgrade or evolve the hero.
When done and you close the hero's page, you are returned to the point of origin and thus if there are more than one hero that needs upgrading then just click on the next hero in line to repeat the process. Or if no other heroes need attention then you can continue with sweeping Dungeon or HBM.