The same certificates for Windows are working fine with MacOS. You have to download the certificate, open it and install. You will be asked for a password of the certificate. You can find it in Signavio Explorer ("Setup" -> "Manage Collaboration Hub authentication").
As the installation of the certificate is complete you can now open the Collaboration Hub:
As a Mac user you will be asked for the password of your Keychain, because the certificate has been added to it. Here use your system password.
More information about certificate installation you can find in our manual.