The Manage GIS Layers window lists all layers either created by your User ID or that are public layers (as indicated by the check mark in the Public? check box). Use this window to review and manage your library of available layers.
To designate a layer as a base map and have it appear in the base maps list in the GIS (Geographic Info System) Explorer window, select the Is Base Map? check box. Only image type layers should be designated as base maps.