After downloading the mql file and opening it in the Metaeditor, you would need to compile it for the EA file to be created. This will add the corresponding EA file right above the mql file in the same folder/location you have your mql file at. You can then transfer/copy-paste the newly created EA file to your MT5 terminal data folder -> mql5 -> experts.
After that close the window and then refresh the experts list in your MT5 by right click in the navigator experts list tab then click refresh. This will bring the new EA in the list ready for you to add to the corresponding chart. I hope this helps.