Audacity 2.1.3
Windows 7 64 bit Home Premium SP1
I’m brand new to using Audacity. Please be gentle with me. I can say though that I just completed a project of getting an LP onto a CD. Took me some time but I figured it out. 
What I want to do now is to adjust the recorded volume levels of music files that I have downloaded from the net. I can get the file into Audacity but don’t know where to go from there.
Any help would be most appreciated.
Dave
Effect → Amplify. Enter an negative amplification number to bring down the volume.
-6dB is a very noticeable change, so that might be a good starting point. You’ll have to adjust by ear (not by the appearance of the waveform) because perceived loudness is related to the average level and the frequency content. (Loudness does not correlate well with peak levels.)
Older recordings tend to be less dynamically compressed (so they sound less-loud with the same peak levels) and the vinyl production/playback process alters the apparent amount of compression (making some peaks higher and some peaks lower) without changing the sound of the dynamics so your digitized vinyl typically won’t be as “loud” as a modern recording with the same peak levels.
Thank you for the suggestion. I’ll be giving it a try.