Selecting the file to play

Server Version#:Version 4.34.4
Player Version#: latest ios

I have a server which shares out it’s files to different players. I have several resolutions of the same file, depending what and where I want to play it.
Plex is having problems streaming 2160p files across the web, I don’t use plex to play these files. How do I specify a particular file to be associated with an entry in plex’s library when there are multiple copies of the same file, different resolutions on the file server?

thanks

click the options menu (the ellipses) on the poster or preplay screen and choose Play Version