On a PC, 'juicebox_lite.lrwebengine' is just a regular folder that you can go inside. However, on a Mac, it is seen as a special package which you would need to right-click and select 'Show Package Contents' to go inside.

Instructions for installing the Lightroom plugin can be found on its support page here.

On a PC, just drag and drop the 'juicebox_lite.lrwebengine' folder onto your Lightroom desktop shortcut.
If, for any reason, this does not work, copy the entire 'juicebox_lite.lrwebengine' folder (not just the contents) to your Lightroom 'Web Galleries' folder: C:\Users\username\AppData\Roaming\Adobe\Lightroom\Web Galleries\

You might need to show hidden files to navigate to this location on your PC using Windows File Explorer.
Otherwise, you can open your Lightroom 'Web Galleries' folder by opening Lightroom, going to 'Edit -> Preferences' (from the drop-down menu at the top), selecting the 'Presets' tab, clicking the 'Show Lightroom Presets Folder...' button and then navigating inside the 'Lightroom/Web Galleries/' folder.

On a Mac, just double-click the 'juicebox_lite.lrwebengine' package.
The Lightroom 'Web Galleries' folder can be found in this location on a Mac: Users/username/Library/Application Support/Adobe/Lightroom/Web Galleries/

On a Mac, all you should need to do is extract the 'juicebox_lite_1.5.0.zip' file, go inside the 'juicebox_lite_1.5.0/adobe-lightroom-plugin/' folder and double-click the 'juicebox_lite.lrwebengine' package.
If this does not work, then it might be worthwhile uninstalling and then reinstalling Adobe Lightroom to see if this helps (although the manual method of copying the 'juicebox_lite.lrwebengine' package to the 'Web Galleries' folder should also work fine).
Also, please make sure that you have Adobe Lightroom v4 or later installed. The 'juicebox_lite.lrwebengine' plugin will not work with Adobe Lightroom v3 or earlier.

If you cannot find Adobe Lightroom's 'Web Galleries' folder on your computer, then please try the suggestion from my post above:

• Open Lightroom

• Go to 'Edit -> Preferences...' (from the drop-down menu at the top)

• Select the 'Presets' tab

• Click the 'Show Lightroom Presets Folder...' button

• Navigate inside the 'Lightroom' folder in the file explorer window that pops up

• Now navigate inside the 'Web Galleries' folder

This is the folder that you should copy and paste the 'juicebox_lite.lrwebengine' package to (when installing the plugin manually if double-clicking the 'juicebox_lite.lrwebengine' package does not work).
If you do not have a 'Web Galleries' folder (although it should exist by default after installing Lightroom), then try creating it manually in your 'Users/username/Library/Application Support/Adobe/Lightroom/' directory.

There should be no need to look inside the package (although it seems strange that you do not see anything inside it).
To install the plugin to Adobe Lightroom, either double-click the 'juicebox_lite.lrwebengine' package or, if this does not work, copy and paste the 'juicebox_lite.lrwebengine' package to the 'Web Galleries' folder (see above).

The 'juicebox_lite.lrwebengine' package is bundled within the Juicebox-Lite zip file.
Extract the 'juicebox_lite_1.5.0.zip' file and you'll find the 'juicebox_lite.lrwebengine' package in this location: juicebox_lite_1.5.0/adobe-lightroom-plugin/juicebox_lite.lrwebengine

The only location that the plugin should be installed to is 'Users/username/Library/Application Support/Adobe/Lightroom/Web Galleries/'.

Sorry. There was an instance of 'juicebox_pro.lrwebengine' rather than 'juicebox_lite.lrwebengine' in my post above (which I have since corrected).

I hope these notes help you to successfully install the plugin.

Edit:
Incidentally, the Lightroom plugin was first bundled into the Juicebox-Lite zip file in v1.4.3.
If you have a version prior to v1.4.3, you will not find the 'juicebox_lite.lrwebengine' package inside the Juicebox-Lite zip file.
You can download the current version of Juicebox-Lite (v1.5.0) from the download page here.

Oh,
and one more thing.

If I need Adobe Lightroom, ... negative. Not buying anything from these crooks again. Doesn't allow me to transfer licenses to a new computer. Need to buy again.

1. everybody upgrades their computers after a few years. Common thing. Not for ADOBE, though. So screw Adobe.

Sorry, no business under such money hoarding conditions.

Definitely helped.
Thanks for the clarification!

I have another issue now, but will open another thread for it, not to confuse.
Thank you