I just got a new Macbook Pro, I used to do my developement on my imac. When I go to upload it tells me I have a valid certificate, I just need to export it and import it on here. How do I do that?
New Mac = No more apps
Go to your old mac, open up keychain. Find the certificate you used for uploading you app - right click and select export.
Enter you password and once done, transfer the newly exported certificate to your new Macbook Pro.
Open up the certificate and input your password.
You can now sign and upload you app from you new Macbook Pro.