Clicking the left or middle mouse button on an entry causes this window to be (de)iconified. The right mouse button brings up the usual Window Menu (unfortunately, the Resize option doesn't work in the normal way).
The Icon Manager can be summoned from the Control menu or by pressing Control-I in the root window. It can be dismissed from Control menu or by pressing Control-H, either in the root window or on the Icon Manager itself.
Note that the Icon Manager window has a Window Frame like any other window, and can thus be manipulated using the normal window menu commands, available by clicking the right mouse button on the frame. Iconifying the Icon Manager may seem strange, but it can be done.
Selecting the Dismiss function is another way to get rid of the Icon Manager. Beware however, that Kill Client or Kill is not a very healthy idea, since the icon manager is an integral part of the TWM system.
