If you have no objects to show yet there are the settings in the ‘Behavior’ tab:
If there are objects the view will zoom to an extent around those objects retrieved from the ArcGIS layer(s).
Please download the Demo project if looking for how to implement a simple map view, it has 6 good examples.
EDIT: It seems you want to load another base map altogether, because the Default X, Default Y and Default Zoom Level are working. You could use for instance this base map (set in Base Default Map URL): https://services.arcgisonline.com/arcgis/rest/services/NatGeo_World_Map/MapServer
Default X = 0, Default Y=0, Default Zoom Level =4 and Spatial Reference= 102100 and you would get: