The PSE files are the firmware (The internal software that gives the aimon its features). Generally the higher the number the better as it will contain the latest features and fixes so If you are already on version 1.8 then you should be OK unless you want the PS/Select switch version. the PSC files are specific settings profiles that Tuact have found to be the best for specific games. they are a good base for tweaking to you own liking.
The process for loading these from the downloaded files is basically the same. All you need to do is start the software, then while holding the button for 2 seconds plug in the dongle to the PC. the software should recognise the dongle and show your current settings. Then it just a matter of going to the firmware or profile pages and clicking load from and choose the file you wish to upload. Then use the dropdown where the firmware or profile choices usually are and you should see one that refers to the downloaded one you selected. Highlight this one and choose save to upload it to the dongle.
With the PSC files, if you tweak them to better suit you you can plug the dongle in in setup mode again and save your custom settings out to your own PSC for easy upload later.
You can also do the same with any custom button mappings you create.
I know it a lot to take on but hopefully this makes sense to you.