Unless there is a strong business justification to add reports on the workspace, it would be better to avoid modifying the workspace and add the required report on the suitable tab of 'Hardware asset dashboard' instead.
To make changes to any workspace, UI builder can be used. Search for 'UI builder' in the application navigator to find it. On opening the UI builder, check under 'Experiences' to find 'Hardware Asset Workspace'. The following URL has details on UI builder. You can try whether it is possible to configure the workspace using UI builder as per your requirement if you actually need to modify it:
https://docs.servicenow.com/bundle/vancouver-application-development/page/administer/ui-builder/task...
