LW 5 Install Folder?

Lightwright will automatically choose the appropriate shared folder, which is used for things that users want to have available by anyone who uses the same computer. It is NOT where approval codes, etc. go. Apple changed the access rules starting with El Capitan.

The registration info goes in different places depending on whether you're using Lightwright 5 or Lightwright 6, and also whether it's an institutional license or a personal license.

To find out where the registration info file goes, launch Lightwright and enter the registration information (registered name, serial number, and approval code) in Preferences/Registration. Then quit Lightwright and search for a file named Lightwright 6 Registration.regi. Wherever that file is, that's where it belongs for that operating system (in your case El Capitan).

Also, note that Lightwright 5 is NOT compatible with macOS Sierra, and never will be (its code is too old), so if you upgrade the lab computers at some point, you'll need to be running Lightwright 6.