If you are configuring the first Oracle instance on a machine where more than one instance is running, you can configure it by following the steps in the Configuring a single instance/multiple instances in VCS section.
The High Availability Configuration wizard will not allow you to configure the next Oracle instance if any of the mandatory dependent resources such as mount point, disk group, disk, and listener are already configured in VCS.
If existing resources are part of the Oracle service group, unconfigure the existing service group and then reconfigure the new instance along with the old instances/listeners which were part of the pre-existing service group.
If existing resources are part of an application service group other than Oracle, the wizard does not support configuring multiple applications. You can configure these applications through CLI or InfoScale Operations Manager.