Open your Library in the steam app.
On the left side, right click "CSGO" and click properties at the bottom.
In the middle click the button called "Launch options"
Paste the following inside it. Be sure to fill in the blanks

-novid -tickrate 128 -high -threads 4 +fps_max 0 +cl_showfps 1 +cl_interp 0 +cl_interp_ratio 1 +rate 128000 +cl_updaterate 128 +cl_cmdrate 128 +mat_queue_mode 2 -freq (Insert Monitors Refresh Rate) -refresh (Insert Monitors Refresh Rate) +cl_forcepreload 1 -nod3d9ex -nojoy


You can find your monitor refresh rate by right clicking the desktop, screen resolution, advanced settings, monitor, and it should tell you right in the middle.