To install the Firefox add-on "Better Gmail 2" and activate the "Folders4Gmail" portion, take the following steps:
[Note: These instructions are outlined using Firefox for Mac. Firefox for Windows functions the same way, and the menus and their names should appear nearly identical]
In Firefox, go to the toolbar, at the top of the web browser, and select "Tools".
In the "Add-ons" window choose "Get Add-ons"
In the "Search All Add-ons" field type in Better Gmail 2.
Choose "Better Gmail 2" and then click "Add to Firefox".
There will be a short delay then click on the "Install" link
In Firefox, go to the toolbar, at the top of the web browser, and select "Tools", then select "Add-ons".
In the "Add-ons" windows, select the "Extensions" tab, click on "Better GMail 2" and then choose the "Options" ("Preferences" if you are using a Mac) button under "Better GMail 2".
Under the "Sidebar" tab check the Folders4GMail box and then click "OK".
The next step is to modify your Gmail labels to take advantage of Folders4Gmail
Before starting this section, take time to consider how you will be grouping and identifying your "nesting" labels.
Create a label (or choose an existing label) which will be the top most label for your "sub" or "nested" labels.
Modify existing labels (or create new labels) which will be your "sub" or "nested" labels - this requires that you use your top most label followed by a "/" and then the name for your "sub" label
If you want to create additional "sub" folders, use the same format
One item to note is that the change to using the "nested" labels can take as long as a day (depending on the number of emails and labels being modified) to be fully recognized and show up in your web browser.