After downloading the zip file you can install it with menu Edit > Preferences > Add-ons > Install (top-right corner), then browse for the zip file and press the Install button.

After enabling the add-on you should customize the preferences. You can hover the mouse over each setting to see a tooltip with more details.

Image of version 0.9.1, with both the panel and header widget visible.

When finished, the panel can be used by clicking on each button to toggle the visibility of that collection, and by holding Shift and click-dragging on the cells to toggle multiple collections.  
A cell with an empty circle icon means that the collection has one or more objects in it, and a cell with the filled circle icon means that the collection holds the current active object. 

The button on the left of the panel, with the eye icon, lets you toggle the visibility of all collections at once. The button on the right is the "Link to Collection" operation, letting you add the selected objects to a new or preexisting collection.