To use the Chem3D commands that you normally see in the Menu bar of the Chem3D application:
To find bond lengths, just put your mouse over the bond of interest.
To change the settings: Point within the windows below and right-click (Windows users) or point within the window above, press and hold the Ctrl key and hold down the mouse button (Macintosh users). Drag the mouse button to the the sub menu of interest and then select from the available commands in the sub menu. The sub menu commands in the Plugin are a subset of the menu commands of the Chem3D application. One useful tool would be "Tools" - "Fit model to Window"