Generator uses metaeditor compiler for final build of your EA or script.
You will need to setup both compiler and output path.

Look for metaeditor compiler in your MT4 or MT5 terminal installation folder.
Compiler is called "metaeditor.exe" or "metaeditor64.exe".

Typical path looks like this:
C:\Program Files (x86)\xxxxxx\metaeditor.exe
Here xxxxxx is your broker name or terminal installation folder.
Output Path
Look for output path for generated EAs, scripts and indicators.
On Windows 7,8 and 10 it is inside C:\Users\ folder under your username.
Find full path using terminal menu: "File" - "Open Data Folder".

Typical path looks like this:
Here xxxxxx is your user name and ##### is long hexadecimal number.

You can find Output Path folder inside terminal "Open Data Folder":

data path

Typical compiler and output setup example below.
Note that Output Path ends with MQL4 or MQL5.

mql options

Edit following parts based on your folders:

mql options 2

This should be enough but if you still can not get it to work check items below:

Play video to see different way to find and setup Output Path for compiler output: