[Changed]Leave the steps but add a separate subsection for the diagram underneath.

https://docs.redhat.com/en/documentation/openshift_container_platform/4.18/html-single/installing_on_oci/index#installing-oci-workflow_installing-oci-assisted-installer

Use the original diagram in version 4.14 as an example: https://docs.redhat.com/en/documentation/openshift_container_platform/4.14/html-single/installing_on_oci/index#installing-oci-about-assisted-installer_installing-oci-assisted-installer 

Assembly:  installing-oci-assisted-installer.adoc
Module:  installing-oci-about-assisted-installer.adoc

Diagram file (hidden in section): 
image::684_OpenShift_Installing_on_OCI_0724_assisted.png[Image of a high-level workflow for using the Assisted Installer in a connected environment to install a cluster on

]