You'll want to leave this middle section clear ( make sure your file is saved as a .PNG )
Fill in the sides on the left and right, the resolution for this is 517 x 1080 [in the 1920 by 1080 format]
Don't worry if you don't play the game in 1080p, you can resize your overlay to scale down to the proper resolution after creation.

*Here's a template for making a layover*
Replace DOTCOM with .com <--

http://www.mediafireDOTCOM/view/e0s5d6bqaf09bc7/monolith_layover_template.png]Blank Template

That's basically all you need to know!
I have created a few so far, mediafire linksget filtered in Steam, so I have to replace the .com with DOTCOM, just make sure you replace the DOTCOM when you copy the link !

Here's an example of what it a custom layover would look like in game
This is one I made to mimic the scanline effect in game*

Any questions, need help?
Feel free to drop a message below, thanks ^^