The COSMOS tested draws on our earlier experience with community research testbeds (ORBIT, GENI) to provide an easy to use testbed interface along with a variety of tutorial, experiment execution, measurement and monitoring tools to provide a good experience through the entire life cycle of an experimental project. In particular, the COSMOS experimenter portal (as shown below) will provide a graphical user interface which visualizes the testbed resources and their availability for the experimenter to select nodes, radio parameters, desired network links and computing resources in both core and edge clouds. The portal will allow users to construct an experiment directly on the GUI screen, or if they prefer, experimenters can directly specify their experiment using the COSMOS scripting language (CEDL). More experienced users have "bare-metal" access to node and compute resources where needed, of course, subject to availability of resources. For the experienced user, the availability of well-defined APIs for each of the testbed's components are key to usability. The COSMOS measurement library is also another important tool for users, facilitating data collection through a set of monitoring and data storage tools.