What graphics card are you currently running? If Nvidia, open the "NVIDIA Control Panel" (accessible via Windows Control Panel or a right-click on your desktop) and on the left-hand side select "Change resolution" under Display. After selecting to change your resolution, on the right-hand pane you should see "Refresh rate" and from the drop-down select 75Hz; if you can select higher, go ahead, otherwise if you don't see 75Hz, perhaps your monitor doesn't support it.
Once you've changed your refresh rate, apply the settings in the control panel and you should be set. If your GPU is not a NVIDIA, please reply back whether it's Intel HD or AMD.
All the best.