Download the Back to Basics Northern Legends package.
Now, choose the level you want to play from the list in the downloads section.
Copy the tr4 file into the data/ folder and copy the script.dat and english.dat files into the main trle folder.
Create a setup link for the tomb4.exe and make sure that Volumetric FX are enabled, unless stated otherwise in the comments section of the level you are playing..
Please take note that Back to Basics Northern Legends is not playable on a Mac.