If i have tow 12-volt batteries and i want to use them together to give me 24-volt. so how i can hooking them ?

yes the answer is to hooking up the battries in series to give you24V.

:Becouse threre is tow type of batteries conection 

   .a- Series connection: which icrease the system voltage   

 .b- parallel coneection : which icreasethe available current flow from the batteries 

For Example this is your12V battery   (+)  -|l-  (-)       

Connect them as    (+) -|l--|l- (-)  

This will give24 Volts.     

series connection to have the addition of both of thier values so12 plus12 equal24 

you have to put them in the series connection

should be the series connection 

should be in serial connection i.e positive of the first connected to the negative of the second and we get24 volts positive terminal at the secnd battary positive and the negative at the first battry negative 

2 condition to get the exactly24 volts these conditions are 

a) the intrnal impeadance of the2 battaries should be the same or the diffrance should not excced10% of each 

b) the same ampere hour for each

best regards

connect betries in series conection and get24 volts

In series connection, i.e. +-+-

in series connection

put tume in series connection its simple.

+-+-

Make a Series connection : connect the (+) pole of Battery1 to the (-) pole of Battery2.