Make sure the Creatures button is selected above the card list to the left.
Find the Creature you want.
Use the filter controls above to narrow down your search.
Hover the mouse over a card to see the card's details.
Click the arrow next to the Creature you want to add to your Legion. Mobile: For some mobile devices, you will need to tap once to see the card preview, and tap again to add the creature. You can also swipe to the right on a creature to quickly add it to your legion.
Your Legion's total cost is listed in the bar above the Legion. Each Creature's total cost, including equipped Upgrades, is listed to the right of the Creature's name.
Then select Upgrades:
Click the Upgrades button above the card list.
Find the Upgrade you want.
Click the numbered button next to the Upgrade containing the number of the creature you want to add the Upgrade to.
If there are no numbered buttons near an Upgrade, it cannot legally be added to any Creature in your legion.
Click "Save Legion" to save your current legion for later, or share it with others.