The easiest way to create a new certificate is to use the wizard, that is included in Passcreator. It is an interactive step-by-step guide that takes you through the process of creating a certificate. To start the wizard, click on Certificates in the menu after you've logged in to Passcreator. Next click on "Add or update certificate" and on "Create a new certificate" on the page that is shown afterwards. Follow the instructions in the wizard to create a so-called Pass Type ID and created a certificate for it.
The steps needed to create a certificate are described below as well if you want to read through the process.
Creating a new certificate
To create a new certificate you need to create a Pass Type ID in the Apple Developer Portal, download a certificate signing request (CSR) from Passcreator and use it to create a certificate for the Pass Type ID.
First, log in to the Apple Developer Portal: https://developer.apple.com/membercenter/index.action
After logging in on the Apple Developer Portal, click on "Certificates, Identifiers & Profiles".
Click on "Identifiers" in the menu on the left.
Afterwards you should see this screen:
Click on "All Types" on the upper right and select "Pass Type IDs".
Click on the blue plus sign next to the headline "Identifiers" on the next page to create a new Pass Type ID.
Select "Pass Type IDs" on the form that is now shown and click "Continue".
Enter description and an Identifier. The identifier should be a reverse-domain name. E.g. if your domain is example.com you should use pass.com.example.my-name
Click "Continue" on the upper right.
Click on "Register" and on the next page to create the new Pass Type ID.
You'll now see a list of all Pass Type IDs. Click on the ID you've just created.
The next page shows a button to create a certificate. Click on that button and Continue on the following page.
The Developer Portal will now ask for a CSR file that is needed to create the certificate. Download it by either clicking on this link https://app.passcreator.com/en/passusercertificate/createcsr or going to Certificates --> Create or update certificate --> Create certificate without the wizard --> Download CSR file in the Passcreator online portal.
Your browser will download a file called "upload-to-apple.csr". Upload this file on the the form in the Apple Developer Portal and click on "Continue" afterwards.
Apple now creates the new certificate and shows a page where you can download it. Click on the "Download" button to download your certificate.
Go back to the Passcreator certificate section (if you should have closed it in the meantime, this is the link that takes you to the correct page: https://app.passcreator.com/en/passusercertificate/new - click "Create a new certificate").
Upload the certificate file that you've downloaded in the Apple Developer Portal (filename should be pass.cer) by selecting that file and clicking the "Save" button.
Click on Save and Passcreator will show you a message that your certificate has been saved.