twaingle

The short story:

You access TWAINGLE from an application the same way you access a scanner or digital camera from that application.

The long story:

The way you open TWAINGLE depends on the application you're using -- just like with a scanner or digital camera.
There is usually an "Insert" or "Acquire" menu or menu option somewhere.

The program shown in the example on the demo page is the OpenOffice word processing application.
The way the TWAINGLE dialog is opened with that app is from this menu:

See? It's just like selecting a scanner.

On that very last sub-menu, there are two options: "Select Source" and "Request". To select TWAINGLE, click on "Select Source". You will get a dialog box that looks something like this:

In this example, there are no other devices (scanners or cameras) installed on the system. So TWAINGLE is the only thing in the list.

Now you just have to select TWAINGLE and click "Select".

You then go back into that same menu and click "Request". TWAINGLE will appear!

Another example:

Here's an example of getting to TWAINGLE in a different application. In this case, the app is the GIMP, a free image editing application.

Click on "TWAIN", and the "Select Source" dialog box will appear.
Again, select "TWAINGLE" and click "Select". This time, TWAINGLE appears immediately.