On the right upper corner of the Map view is the menu of Legend. Click the triangle button to close and expand the Legend menu.
To edit the Legend, expand the Legend menu, right click to open the context menu and then click Edit Map Legend.
This will pop-up the Map Legend editing window to allow users to add or remove legend components. Click the button to add a component to Legend. Click the button to remove a component from Legend.
Please note that to refresh the legend open the Map Legend editing window and then click OK.