IF your talking about Single Player, you have to play through the game until you beat the second tier of missions and play through the special Vjun level and you can pick single saber and learn the last style or chose duals or staff.
Or, you could just type the saber command in the console, like saber dual_1-5 (gives staff).
The different numbers are for various hilts (like if I want vanquisher I'd type saber dual_5 and press enter).
For two sabers via console saber single_1-9 saber single_1-9 (for example, saber single_1 saber single_1 then press enter).
Your auto-blocking is in vain! Only SP source code modification can allow you to block my desann-style attacks without being staggered now!