Create a directory, namely democa2, for the second realm inside /etc/openxpki/config.d/realm.

Copy the /etc/openxpki/config.d/realm/ca-one sample directory tree to a new directory (cp -r /etc/openxpki/config.d/realm.tpl/*/etc/openxpki/config.d/realm/democa2) within the realm directory.

In /etc/openxpki/config.d/system/realms.yaml, update the following section:

# This is the list of realms in this PKI
# You only need to enable the realms which are visible on the server

democa:
    label: Verbose name of this realm
    baseurl: https://pki.example.com/openxpki/

#democa2:
#    label: Verbose name of this realm
#    baseurl: https://pki.acme.org/openxpki/

# This is the list of realms in this PKI
# You only need to enable the realms which are visible on the server

democa:
    label: Example.org Demo CA
    baseurl: https://pki.example.com/openxpki/

democa2:
    label: Example.org Demo CA2
    baseurl: https://pki.example.com/openxpki/

Save the file.