It depends on the file that you downloaded, they're all different. If you have to download 2 "sound" files, the creator put the first batch of wav files in the 1st zip file and the 2nd batch in the other zip file + the sound.cfg.
Here's how I installed my sounds:
I created a new folder in the aircraft folder, where I place all my sound files. This avoids using too much disk space. I called the folder fsfsconv, then I created a directory for my 747 sounds in it. I then placed all the wavs + the sound.cfg in the 747 folder. When I want one of my 747s to use the sounds, I will go to its sound folder, open up the sound.cfg and write under [fltsim]: alias=fsfsconv\747 sounds . This is the directory for the sounds.