This tutorial covers using Fantastico with Site5, but the procedure for other hosts should be very similar.
From the Site5 Dashboard:
Scroll down to “Software/Services” and click “Fantastico”
Click “Launch Fantastico”
Click “New Installation”
Fill in the information on this page:
Install on domain – select from drop-down menu
Install in directory – leave empty to install in the root directory, or choose a directory name (the directory will be created for you).
Admin access data:
Username – whatever you like
Password- whatever you like
Admin nickname – whatever you like
Admin e-mail – whatever you like
Site name – – whatever you like
Description – optional
Click “Install WordPress”
Click “Finish Installation”
Click on the link to your site
Once you login, you can start getting your blog or website up and running.