tap on their portrait and slide in a certain direction. After that, the character will attack depending on the direction you slid your finger in.
The story in Bravely Archive revolves around mysterious crystals, sought after by two opposing organization. This conflict is central to the game, requiring you to go through tons of dungeons and fight against hundreds of enemies to get the crystals everyone so desperately wants.
Bravely Archive is an excellent JRPG with the typical production value for a game from Square-Enix. It also has an amazing soundtrack, extraordinary graphics, and plenty of quality content.