This assumes:

• You have an ArgoCD server up and running. If not, check out my article Install Red Hat OpenShift GitOps Operator using the console (Argo CD)
• You have installed the ArgoCD CLI.
• You are able to log into ArgoCD using the CLI. If not, check out my article Log into ArgoCD using the CLI on OpenShift

The argocd proj list command can be used to list your ArgoCD projects.

~]$ argocd proj list
NAME     DESCRIPTION  DESTINATIONS  SOURCES  CLUSTER-RESOURCE-WHITELIST  NAMESPACE-RESOURCE-BLACKLIST  SIGNATURE-KEYS  ORPHANED-RESOURCES  DESTINATION-SERVICE-ACCOUNTS
default               *,*           *        */*                         <none>                        <none>          disabled            <none>
my-project            *,*           *        */*                         <none>                        <none>          disabled            <none>

The argocd proj delete command can be used to delete an ArgoCD project.

argocd proj delete my-project

Or in the ArgoCD console, at Settings > Projects, select the project > Delete.