1. Developer certificate (p12)

Use a Mac. Follow these instructions.

2. P12 password (P12_password.txt)

You might get asked for this while creating the P12 file.

3. Development provision profile (vendor.mobileprovision)

You need this only for the test app. Not for final distribution.

4. App ID (com.vendor.module)

This is the Source Code main module name. Developer can give this to you.

1. Login to the developer account.Go to the Certificate section. Its easy to find on the left hand side.. 

2. Create a new Certificate. You need to do this from a Mac. Click the Create Certificate button. Follow the steps. You will be asked to upload a Certificate Signing Request (CSR). This is the P12 file. Use these instructions to make the P12 file.

3. Once you finish the Certificate Wizard, you will get a certificate file downloaded.

4. Give the certificate file to the Developer who has the source code. The source code editor is called XCode.

5. The developer must login to XCode using the same Developer ID used to generate the Certificate.

6. Open XCode in Build Phase - Under the Build Rules assign the Certificate. Complete the Packaging of the file.

7. Developer Pushes package to app store from XCode. 

8. Once the package push is compplete, login to the browser to the developer portal again. You should see the uploaded Package there. Not sure which section. May take upto 10 minutes to see the file. Add description and other stuff has to be filled.