Sorry but the only thing I can help is about the .asc file. It's used for verify that the .exe you downloaded is the original one, that no one modified it, injected some malware or something like it.
It's a digital signature used in PGP. You can search more about it online looking for PGP or GPG. For Windows look at Kassandra, it's a program for encryption and digital signature verification that uses PGP.