Hi Alastair Ferguson,
To use this software you will need to import your tables from WordPress database to your Joomla! database. To do this, just simply log in to your phpMyAdmin on your hosting server, open your WordPress database and click on button "Export". It is really important to first open database then click "Export". After this, open your Joomla! database via phpMyAdmin again and click on button "Import" and select file you have got by clicking Export in previous step. Check out your database prefix too. You will see something like this: "wp_users" for an example. Here, "wp_" is database prefix. So lets put this whole story in steps:
1. Open your WordPress database in phpMyAdmin
2. Click on button "Export" -> then button "Go" , download of file should start (file will be named something like "database_name.sql")
3. Open your Joomla! database in phpMyAdmin
4. Click on button "Import" -> select downloaded file -> click button "Go" and while doing it, check for database prefix if you aren't sure which is your db prefix
After doing all of this steps, simply run your CMigrator, create Configuration profile (you will see there which data you need to fill). And click on button "Migrate". You will be asked to select configuration profile, select one you create, and then see the magic.
I hope I manage to help you. If you have any question, feel free to ask.
Cheers