How do I activate FreeSync? (AOC AGON AG241QX and R9 270)

Hello, I just bought a new monitor compatible with FreeSync but Radeon Crimson doesn't let me activate it. I have the monitor connected via DisplayPort and I installed the drivers (I didnt install the extra things like i-Menu or e-Saver) and the freesync option keeps unavaible. I tried connecting it via DVI too and it keeps being unavaible. How can I turn it on? I have Crimson updated too

(Sorry bad english)