As a dashboard author, once you have signed into your ArcGIS Online organization the beta will be available from the App Launcher as Dashboards Beta.
Most dashboards will open without issue in the beta. However, there are some known limitations with supported browsers, layer types and pop-ups. For a complete list of limitations, see the ArcGIS Dashboards Beta known limitations guide.
When the ArcGIS Dashboards Beta release moves to General Availability, how many versions of Dashboards should users expect to see from App Launcher?
ArcGIS Dashboards Beta will move to being the default version of ArcGIS Dashboards after the beta period. The current version of ArcGIS Dashboards will then move to being ArcGIS Dashboards Classic.