ol/control/WMSCapabilities is a control to load WMS layers on ol maps.
It displays a dialog to select the service you want to add using getCapabilities of the service.
Some services may not respond correctly because of
CORS policies
and you may have to use a proxy to access the getCapabilities...
Listen to the
load event to get the selected layer or options to create it.
Look at the console for the layer definition to insert into your code.