How do i study for the asvab test?

im a 14 year old african american male, and i want to study to become a marine or join the army, i want a combat position, and ive already decided that this is the career choice for me, i have an iq of 125 and i am very determined, i was wondering if anyone had any tips on how i would go about doing this, and before you start to think im doing this because of a video game, im not, im doing this because i want the respect and the duty of being in the military, and serving my country, and im going to high school, so im gonna take jrotc, thanks, i look forward to some good advice :)