When it's your turn, scroll through the skill list. when you find the skill you are looking for, type in the number to the left of the name in the box at the bottom of the screen and press Enter. Once you've done that, put in the number of the enemy that you want use it on. Their heath and number is at the top right. In the first number in the name is the average damage. the second is the mana cost. the numbers at the bottom are the players' health and mana are displayed at the bottom of the screen. If the game glitches up, just restart it.
I don't think anyone on Scratch has done anything like this game. It may seem confusing, but give it the chance and it is very fun! 25 Jul 2014 Fixed bug where P1 wouldn't die. 22 Jul 2014: Fixed bug when you view the credits and you can't play.