Once installed the plugin, select the name of the currency you want to use. Visit the Actions page to define the number of credits you want to award for various actions. The plugin is ready to use out of the box but to do anything useful with it you need to explore the features.
MoolaMojo works for registered users in your site. If you want users to register freely you need to enable "Anyone can register" option on the General Settings page of your WordPress dashboard.
Please have a look also at the internal Help page under the MoolaMojo menu.
Developers who want to extend the plugin will receive our full support. Let us know if you want to suggest action hooks or have a question about the internal organization of the plugin.