You can add, delete and manage iOS Certificates and Provisioning Profiles manually using Appcircle. There is also an easier way. By linking your Apple Developer account to Appcircle, you can see a list of certificates and provisioning profiles and pick the ones you want to use for building and distributing.
To link your Apple Developer account, you need an App Store Connect API Key from Apple's App Store Connect Panel.
Go to https://appstoreconnect.apple.com and login with your account.
Once the team is correct, select Users and Access from the menu:
After navigating to Users and Access, you will see 4 tabs next to the title. Select the Keys tab. Then make sure that App Store Connect API is selected from the list on the left.
To generate a new key, press the + button.
A modal popup will ask you to enter a name and add roles for this key:
After generating the key, download the key file by pressing Download API Key next to it.
Adding a key to Appcircle is pretty easy. Go to your organization by either selecting the bottom left button from the toolbar, or picking it from the menu:
On the Organization screen, select Add New on App Store Connect API Keys list item:
On the form, upload the .p8 key file downloaded from App Store Connect:
Fill in the rest of the form. You can find the Key ID and Issuer ID from App Store Connect Panel here:
Copy and paste them to the form in Appcircle, give it a name, and save.