What do I need from my certificate to use SSL in .NET?

Question

The server mode SSL must use a certificate with the associated private key.

I have my Base64-encoded .crt file and another huge text file with lots of info, from my certificate provider, which includes the private RSA key in an equivalent format.
I tried putting that in a .pvk file to later make the .pfx one, and it didn't work. (nice try, right?)
What do I need to actually do to use this certificate to use SSL in my .NET application?

Edit: Made a proper .pvk, made the .pfx, still, same error.

Answer 1

I finally solved this. I had to use System.Security.Cryptography.X509Certificates.X509Certificate2 with the .pfx file. The simple X509Certificate didn't seem to work.