To battle, it's simple. It goes turn by turn. First, you need to ask the other character to fight. If he wants to, the challenger is the first to attack.
To attack, it easy, in your "Character stats" you will see a place where it's writen 2 number and a D. The number before the D indicate the number of dices you use. The number after the D is the number of faces the die has. At start you have 1d4 that mean you use one 4 faces die and the number you will see is the number of damage you do, but your ennemy can change your damage rate with Def.
To Def the same thing than Attack, but go see the Def in your "Character stats". If you have 0 you can't Def. If you have some Def you can roll it after your ennemy Atk. The number you roll on the Def die is the number of damage your decrease on your enemy's attack.
*IMPORTANT* : When you see, for example, 1d4/2, it means that you must divide the number on the dice. Ex.: 1d4 = 4 = 2, 1d6 = 3 = 2, 1d10 = 5 = 3, etc...
Each time you've been attacked, you lose the number of Hp indicated by this. (ATK-DEF=Hp lost)
If you reach 0 Hp, you lost.
You can also use magic that cost Mp, if you have not enought Mp, you can't use magic. Every Magics are described in your Special in your "Character stats". At start, you don't have any.
Good fight!