Missing .DLL with windows

The problem isn’t with building it but when I share the game people tell me they need some .DLL which is from vcredist_x86 or x64

How do I know which one is the correct one to package with my game?

One option is to point them to the UE4 prerequisites installer which can be found in your engine install directory here: UE4/Engine/Extras/Redist/en-us/UE4PrereqSetup.msi