Product review (3 stars): Here are instructions from Insinkerator
These instructions are a bit jumbled, as the parts labeling is mixed up, and they refer to a single-bolt flange, which isn't in the package.  In an email they said to soften the flanged end of the tube in hot water before slipping on the metal flange.  But they didn't answer my question of why the instructions aren't included in the package.

"Flexible Discharge Kit

The kit consist of the flexible tube A, a single bolt type rubber tailpipe gasket B, a flanged
washer (side view, used on threaded discharged disposers) C and a two bolt tailpipe flange
(colored red) D.

The single bolt type rubber tailpipe gasket B is placed on the flange of the flexible tube A just as
one would place it on the tailpipe used on a single bolt disposer.

If the disposer is a single bolt model, one is to use the existing single bolt tailpipe flange that
came with the disposer.

If the disposer is a double bolt model, one is to use the red two bolt tailpipe flange D included in
the kit.

If the disposer is a threaded discharge model, the flanged washer C is placed against, into the
flexible tube A just as one would place it onto the tailpipe of the threaded discharge models, one
is to use the existing tailpipe nut.

The double bolt flange in this kit is colored red to distinguish it from the silver metal double
flange. The red flange center hole is larger (same size as the single bolt center hole). This
allows for ease of inserting the flexible discharge tube and allows for use of the single bolt
rubber tailpipe gasket."