Since installing an Operator is typically a one-time task, I find it much easier to use the console instead of the command line. 

Go to Operators > Operator Hub and select the Red Hat OpenShift GitOps Operator.

Select Install.

I typically just go with all the defaults and select Install.

You should next see this, the Operator being installed.

And if all goes according to plan, something like this should be displayed.

You should now be able to open the GitOps Argo CD console.

If you get "Application is not available" check out my article FreeKB - OpenShift - Resolve "Application is not available". This may be some issue with the URL being exposed by the route. The install should create a number of resources in the openshift-gitops namespace, including two routes.

~]$ oc get routes --namespace openshift-gitops
NAME                      HOST/PORT                                                              PATH   SERVICES                  PORT    TERMINATION          WILDCARD
kam                       kam-openshift-gitops.apps.openshift.example.com                               kam                       8443    passthrough/None     None
openshift-gitops-server   openshift-gitops-server-openshift-gitops.apps.openshift.example.com           openshift-gitops-server   https   reencrypt/Redirect   None

You can describe the route and ensure:

• The route is exposed on a router - if not, you probably will need to label the route (FreeKB - OpenShift - Label a route using the oc label command)
• The route is forwarding requests onto the gitops server service
• The route has an endpoint

~]$ oc describe route openshift-gitops-server --namespace openshift-gitops
Name:                   openshift-gitops-server
Namespace:              openshift-gitops
Created:                10 days ago
Labels:                 app.kubernetes.io/managed-by=openshift-gitops
                        app.kubernetes.io/name=openshift-gitops-server
                        app.kubernetes.io/part-of=argocd
                        route-type=internal
Annotations:            openshift.io/host.generated=true
Requested Host:         openshift-gitops-server-openshift-gitops.apps.openshift.example.com
                           exposed on router default-router (host router-default-router.apps.openshift.example.com) 4 minutes ago
Path:                   <none>
TLS Termination:        reencrypt
Insecure Policy:        Redirect
Endpoint Port:          https

Service:        openshift-gitops-server
Weight:         100 (100%)
Endpoints:      10.131.0.37:8080

You should see the Argo CD console. You can now log into ArgoCD.

• FreeKB - ArgoCD - Log into ArgoCD using the CLI on OpenShift
• FreeKB - ArgoCD - Log into ArgoCD on OpenShift using the console