My new weekend job. The part you bought is located behind the glove box. It is feed by a vacuum line that runs under the battery and that line is know to rot from the battery being just above it. You must remove the glove box to get at the part you bought. That vacuum valve box attaches to the air switchover valve. It is all part of the heating system. I would check that vacuum line under the battery before tearing into the glove box removal job.
I don't know if you might have access to that valve box you bought from the bottom: maybe take a look at removing the air filter and blower. It may be easier than getting the glove box out. I'm just not sure which would be easiest.