A folder named Bloom is added to your computer when you install the program. It contains one or more subfolders. Each of those subfolders is a collection. It stores the books and stylesheets.
Go to your Bloom folder.
Windows® - My Documents\Bloom or Documents\Bloom
Linux - /home/<user name>/Bloom.
Look for the subfolder that has the same name as the collection and then copy that subfolder to a USB Flash Drive (or a similar device).
On the other computer, connect the device.
Copy the subfolder to that computer.
You can put it in the default folder or in another place.
Find it with the Browse for another collection on this computer command, if necessary.
Essentially, each Bloom book is a little database of texts in various translations, ready to be displayed either in the prompting box, or in the text itself. An interesting implication of this design is that any local language book can become a shell book for other languages; the formats of a shell book and local language book are identical.