In the Files & Memory preferences pane you can find the full path to the User Extensions folder. Open this folder in your system file browser.

In the User Extensions folder (1) there may or may not be an Externals folder. Create the folder if it doesn't exist. Add your external to the Externals folder (2).

Open the Externals.txt file (1), creating it if necessary. You need to add one line to this file that tells Revolution about your external. The line contains 2 items. The 1st item is the name of your external as it appears in the externalPackages property (2). In this example I'm using the EnhancedQT external so that name is EnhancedQT. The 2nd item is the name of the external file (3). Save the file and close.

Also in your User Extensions folder is a Runtime folder (1) that you can create if necessary. This is where you put the version of the external that should be included when building a standalone application. Place a copy of the external in the platform folders that you want to include (2). Note that for OS X the external is in the Universal folder. That is because the EnhancedQT is a universal binary.

Quick Tip: If you have to create this folder then note the folder structure in this example. The folder structure mimics that of the Runtime folder that sits alongside the Revolution IDE engine.

Update the Externals.txt file for each platform.

Now that you have installed the external launch the Revolution IDE. Type the following in the Message Box:

put the externalPackages of stack "home"

You should see your external listed.

When you open the Standalone Settings for a stack your external should be listed.

If you select your external to be included then when you build a standalone application Revolution will copy the external to the proper locations. Revolution also creates a substack named revExternalLibrary that is attached to the stack you used to build the standalone. If you check the externalPackages of stack "revExternalLibrary" then your external should be listed. Note that this stack is only created when you build the standalone.