If you are using Windows 10, then follow these steps:-
1. Open Display settings by right clicking on desktop and clicking on Display settings.
2. Then click on Advanced display settings.
3. Then click on Display Adapter properties.
4. In the new windows, select the Monitor Tab, from there you can change your Screen Refresh rate.
5. If you can't select 144hz then update your monitor drivers and try again after restarting.