To Evolve Pokemon you need both the base and evolution figure. To find out if the Evolution is available select the 'Decks' icon from the bottom of the main menu's navigation and then the 'Edit Figures' button when you have choosen a deck that you’d like to modify. The dots that can be seen under the first four Pokemon (image below) indicate that they can be used as part of an evolution chain.
The advantage of evolving Pokemon is they tend to be more powerful ( 10 damage to normal (white) and gold attacks and an extra star to purple attacks), the disadvantage with evolved Pokemon though is they tend to have less MP (Movement Speed). If you have the base figure and its evolved verson in your deck you can choose the base form and evolve it mid-battle. To be able to evolve you must first either knock out or move an opponent’s Pokemon so the following pop up window appears.