Open this in a text editor, then scroll down to the entry which states ' EnableDebugMenu 0' and change it to ' EnableDebugMenu 1', before saving your changes.
Head to the \Documents\My Games\Sid Meier's Civilization VI folder, or wherever the game is stored on your PC, and find the AppOptions.txt file. There is a debug menu built into Civilization 6, but before you can use it you need to do a quick bit of tinkering in the files to activate it.