Hold your Shift key and right click on the file. You should have 'Open with...', and then probably you'll have some option to use the recommended application only (untick it).
If you still can't see your software in the list, type in your file selection popup (depending on your system, you should click on 'Browse...' to see the Select Folder Window):
*.*And press Enter. It'll enable all the extensions to look for.
