put the resurrect spell in one of the top active spell slots, and click on it to make it the default spell, then take mouse over to the fallen heroes portrait icon and the pointer should turn blue or something like that while over them and right click i think is how i do it, not sure about the mouse button though could be left, but it works well when using the portrait icon. im winging this from memory and not in game, so take this with a gram of salt or whatever the saying is. maybe someone else can confirm this for us.
put the resurrect spell in one of the top active spell slots, and click on it to make it the default spell, then take mouse over to the fallen heroes portrait icon and the pointer should turn blue or something like that while over them and right click i think is how i do it, not sure about the mouse button though could be left, but it works well when using the portrait icon. im winging this from memory and not in game, so take this with a gram of salt or whatever the saying is. maybe someone else can confirm this for us.