A simple way of finding the affinity 2 executables and of telling other applications where the executable is, can be found here https://www.youtube.com/watch?v=MzJlTi8b4Rs
That link doesn't always work. The gist of this guy's method for Windows is: first run the affinity application; next start task manager; right click on the Affinity application in processes to get a drop down menu in which one of the items is "open file location". Clicking on this will show the directory in which the executable resides. The executable is listed in this directory. Right click on the executable and select "copy as path". In software like Photo Mechanic Plus, for example, paste this path as the file location and the software will now be able to find the Affinity executable.