To be OP on your Minecraft server, you have a few methods.
1) Enter an OP command in the console of your manager
Enter the command from the panel :
op NICKNAME
2) Enter the command from the game; an OP can gives the OP right to another player
Any OP player can give the same right or deop another player with two simple commands :
/op NICKNAME: gives the OP status to a player
/deop NICKNAME: delete the OP status to a player
Need advanced rights? Switch to a permissions system.
If you wish an complex permissions system such as PermissionsBukkit, GroupManager or PermissionsEx is more complicated as it's based on groups.