Detailed Version:
CON (Constitution)This stat is very important for any type of fighter. The higher it is, the more longer you can stand in a fight.
Constitution gives you Health, each point will give you 10 Health.
Ex. If a player has 10 CON, then it's 10x10 = 100 Health.
If a player has 73 CON, then it's 73x10 = 730 Health.
STR (Strength)A stat that is very useful for people, that wish to kill their opponent as fast as possible. It can increase your power and dealt damage greatly! Strength gives you extra damage, each point will give you +2% to your damage.
Ex. If a player has 10 STR, then it's 10x2 = +20% Damage
If a player has 73 STR, then it's 73x2 = +146% Damage
How to calculate your total damage? It's easy!
 Spoiler:

Let's say you have 25 STR and you use a jutsu that deals 250 damage. Since there are 100 percents, we will divide 250 with 100. (250 / 100 = 2,5)
This means, that 2,5 is 1% of the jutsu damage.
25 STR is +50% damage. So we will take 2,5 times 50 (2,5 x 50 = 125).
And there we have! Now you put your result together with original damage (250 + 125 = 375)
If you still have problems. This might help you:
(Jutsu Damage) divide with 100 = (Result 1)
(Your STR) x 2 = (Result 2)
(Result 1) x (Result 2) = (Result 3)
(Result 3) + (Your jutsu Damage) = The Damage you deal
If you STILL have problems, just ask a staff member to help you
WIS (Wisdom)Wisdom is important, if you don't wish to spend money on chakra pills. It also gives a bit damage bonus Wisdom gives you more chakra and ninjutsu damage, each point will give you 5 chakra and +0.5% damage.
Ex. If a player has 10 WIS, then it's 10x5 = 50 Chakra
and 10x0.5 = +5% damage.
If a player has 73 WIS, then it's 73x5 = 365 Chakra
and 73x0.5 = +36,5% damage.
DEX (Dexterity)Dexterity is very useful for Taijutsu users. It increases your speed and energy. Each point will give you 5 energy and 1 speed.
Ex. If a player has 10 DEX, then it's 10x5 = 50 Energy
and 10x1 = 10 speed.
If a player has 73 DEX, then it's 73x5 = 365 Energy
and 73x1 = 73 speed.
A player starts with 10 Stat Points, that they can distribute across the four stats, the way they want.
Each time you level up, you get +10 to all stats. And also, you get 10 more stats, that you can distribute across the four stats.
Ex. If a player is level 1 with stats (5 CON, 1 STR, 3 DEX, 1 WIS), and he levels up to level 2. Hes new stats will be (15 CON, 11 STR, 13 DEX, 11 WIS) and he also gets 10 more stats, that he can put any way he wants.
Let's say the player wants to put 5 to CON, 3 to WIS, and 2 to STR. Then hes new stats are (20 CON, 13 STR, 11 DEX, 14 WIS)
Feel free to ask questions!