Handling Amplitude

I have 2.0.6 I downloaded recently. I don’t think it was zipped. I’m using System 7. I recorded in stereo (didn’t want to, but the Radio Shack digital recorder did it anyway) with an electret condenser mike and the volume is too loud. There are quiet parts though so I’d ideally like to bump up the quiet conversation (it was a large, meeting room discussion) and attenuate the louder segments. Can that be done and how? Is that called compression? Also, I assume that if I change it to mono then the file size would be smaller.

Yes, or to give it its full name “dynamic range compression”.
It should not be confused with “data compression”, which is “making files smaller”.

There is help for using the Audacity Compressor in this part of the manual: http://manual.audacityteam.org/o/man/compressor.html

That depends on the format of the file.
For “uncompressed formats” (talking about “data compression” here), such as WAV or AIFF, changing from stereo to mono will approximately halve the file size.

Compressed formats (such as MP3, OGG, AC3) are defined in terms of the number of data “bits” per second. For example, the default setting for MP3 export is “128 kbps” (128 thousand bits per second). 1 minute of audio at 128 kbps will be about 960 kB whether it is mono or stereo. However, if it is mono, then all of the “bits” are used for just one channel, so the sound quality should be better than for a stereo track. If file size is important, then converting to mono and reducing the “bit rate” will produce a smaller file.

Note that while working (editing/processing), you should keep files in (large) uncompressed formats. Compressed formats reduce the quality and that loss cannot be recovered, so avoid file compression until the final export of the completed project.