go to the attack equip screen in battle or nonbattle and look at the top of the screen for manual or semi auto ( wich allows the npc part of the charactor block for you)
do that with the charactors you have to play with!
hope I was of help! ^_^

In the menu screen, make sure that you select TECH. Once you're there, you change the settings at the top from "Auto" to "Manual". Make sure the character you want the second player to play... is listed second on the character screen. Lloyd should be at the top for the first player to play and the second player will play the one under Lloyd. This goes for the third and fourth player as well (if you want to play with 4 characters at once). Otherwise, make sure the other characters are set to AUTO so that the computer can play the remaining characters for you.