In Arma 3, activate the mod by going to Mods and selecting Tacview Recorder
Arma 3 - Mod Activation
Launch the game and go to Options → Game Options, select Tacview Recorder from the ADDON drop-down menu, and choose a Recording output directory that Arma 3 has permission to write to, such as such as %USERPROFILE%\Documents\Tacview.
Arma 3 - Game Options
Terrain
To add terrain textures and terrain elevation files in Tacview, follow the instructions in the video
You can find all the ARMA maps for Tacview on Tacview content.
Since this video was made we have added an ARMA terrain layer, so go to Options → Terrain to make sure the terrain is set to Auto or ARMA (not Enemy Engaged: Comanche vs. Hokum as instructed in the video)