Command /usr/bin/codesign failed with exit code 1

Hi,

I've been following an online course to develop my PDF magazine into a an app for the newsstand. Ive created the app in xCode and done everything iTunes connect except upload my build. When I try to archive my app I get the following error code.

1BC6018A37967FD1C94BF8168C41B5B534FF50C7: no identity found

Command /usr/bin/codesign failed with exit code 1

I have been doing a lot of googling and I have found a few solutions but none of them work for me or are too complicated for me to follow. Im under the impression it has something to do with certificates.

Some people have said the certificate may be out of date. This is the first app I have built so it can't be that but I tried anyway and revoked the certificate re did them and setup new provisional profiles again and it didn't work.

A lot of people have said it had something to do with "Apple Worlwide Developer Relations Certification Authority" certificate and that it should be set to default. I have checked and mine is set to default. One thing I am wondering is was I supposed to do something with this certificate in the first place.

Thank you in advance for your help and be warned I'm a complete novice when it comes to this so I will need step by step instructions. Apple have been no help in this matter I might aswell have phoned my gran.

Cheers