First use the codes on this site (it should considering that these codes work if you emulator does accept AR codes.) http://www.gamefaqs.com/console/snes/file/564404/14784
For Example if you wanted to max sigurd's strength put 7e2d41** in the enter code box(the** means how much you want to set it to) so it would come out as 7e2d4199 and add then click add code and then it should work.
(Note: some of the names are different than your rom and some of the codes for characters are wrong. so you might have to do some trial and error if you want to use codes for your second generation characters.)