Downloads and installs the Apple code signing certificates and provisioning profiles.
The Step installs those .p12 certificate files and provisioning profiles that you uploaded to your app's Code Signing tab. You can upload multiple versions of any code signing file.
By default, the Step requires no configuration. To be able to use it, you only need to upload a .p12 certificate and a matching provisioning profile to the Code signing tab.
However, if your certificates have passphrases, you need to make sure that passphrase is available for the Step.
Similarly, you can set the path to the Keychain that should be used in the Keychain path input, and set a password for the Keychain in the Keychain's password input.
In the case of most code signing issues, it's the Xcode Archive & Export for iOS Step that fails, not this one. If this Step fails, there's a couple of things you can do first.