The error is telling you exactly what is wrong. Your cert is missing vital information. The only thing you'll be able to do is provide the error to the issuer and request a new cert.
If you want to be extra thorough, google some examples of a certificate online and compare them to the text in your cert to make sure they have the same format before you request a new cert. That way, if they tell you you're wrong or give you any grief, you have something to show them.
That can backfire as well though, you may determine that your cert actually does have the correct information and SF is just being picky. In which case, you'll have to open a support ticket.