Without the following things, you will have trouble using PamelaWare for WordPress. If you already have a working system, just install the plugin and we'll tell you what if any of these pieces you might be missing, and point you to help if we can.

1. WordPress 2.0.7 Installation:  Obviously you need WordPress up and running before you can install Pw-wp - right now, this plugin works on version 2.0.7,  as version 2.1 updated the login page and I haven't looked at how to integrate with the new design yet.
2. Clock Synchronization: For security reasons, login will fail if the timestamp in the data sent by the identity selector is not reasonably close to the system time of the WordPress system. We strongly recommend that you consider using NTP to synchronize your system clock to internet time.
3. PHP Version 5: PW-wp uses the PHP 5 Dom extensions, and as a result this plugin is not compatible with PHP version 4.
4. SSL Private Key & Passphrase knowledge: You must have an SSL certificate, and you also have to be able to tell this plugin what your Certificate private key and passphrase are, so that it can decrypt messages encrypted by the Identity Selector.
5. Mcrypt & OpenSSL PHP libraries: These libraries are used within the plugin.