Can't import into keychain

I am new. I inherited a half finished app. I successfully finished it in flipabit and got the app into Google Play with no problem. I am having a horrible time with Apple. The app had been rejected so many times by Apple, I decided that I would create a total new bundle.I have the Cert for signing, the mobile provision key, the Apple Distribution.cer , and an authorization key. I can't import any of them into keychain. I am thinking that that all these were created by someone else for the original app and I can't import any of mine, though that really doesn't make sense. Any and all ideas would be truly appreciated. I have been looking into upworkk to have someone do this for me but I am wondering how in the world they could do that.