1. First see which missing file you needed to run your game or application and then copy that file name include .DLL extenstion.
2. Paste the File name on google and download that missing file. Websites like DLL-files.com is the large source of DLL files and this site most of the time provide you correct DLL file. It will give you a .zip extenstion file, you have to extract that file and paste the DLL file to the following path :-
After pasting the file on this path, restart your system and again try to run your game or application.