How do you install the lens in a 35 Terraplane headlight?

From the manual:

Loosen the screws at the bottom of the lamp body. Push the bottom of the
lens backward and downward until the top of the lens is clear of the top of the
lamp body and lift out. Replace by reversing this operation.
Do not touch the reflector, as any marks will reduce the illumination.
Should it be necessary to clean the reflectors, use ordinary lampblack on a soft
cloth and wipe gently in a circular motion.
If the reflectors require frequent cleaning, it is an indication that the gaskets
are not giving a proper seal and they should be replaced.

I would add that it is CRITICAL that you place a blanket or two under the headlamp, sitting on the fender and bumper, to catch the lens if you should fumble during the lens removal / installation.  These lenses are not easily replaced and you WILL drop one, at some point.

By the way, there's a '35 Terraplane manual in our on-line library (at the H-E-T site) as well as a complete shop manual for '34 through '39, I believe.