There's no built in import/export feature yet, but you can do it manually.
Take a look at this folder (replace your user name):
You will find a Config.xml file. You can copy this file to same location on another computer with FJ installed.
If you need to merge one computers rules with anothers, you will need to edit the configuration files and copy each <rule> segment to the other file, to create one with all rules. It's rather simple if you are just a little familiar with XML, and not to hard even if you are not.
The import/export feature is on my todo list.