Hi BEM,
You are absolutely correct in your assumptions. You can only download the Little Reader to your PC and then purchase iAccess to have the entire curriculum on your iPad. Once you click on the software trial tab you will see a green rectangle that says Download Little Reader (English US) - click on that and then follow the prompts. After downloading the software, double-click on the file to start installation.
After installing the software, you will automatically be able to use the program for 14 days.
You might be able to find out why your PC is running slow by running a check through your anti virus program.
There are some suggestions on this link.
http://www.computerhope.com/issues/ch000179.htm