The second card must be of an equal or lower Stage than the first card

In order to evolve a card, a few requirements must be met:

You must have two cards with the same name, cheap coc gems  thus from the same evo tree. Example: Goblin+ with Goblin can evolve to Goblin++.

You must have enough Rupies to pay for the evolving cost.

The second card must be of an equal or lower Stage than the first card. Example:  cheap coc gems You can evolve a Goblin+ with a Goblin, but not the other way around.

Click the Evolve button at the bottom menu or on "My Page".

Choose a card to evolve. It will be evolved to the next form.

Choose a evolver card.  cheap clash of clans gems It will be sacrificed.

Click on "evolve" and watch a quick little scene.