The Definitive Guide to Data Quality
Instead of using the format of "<packagename>_<modulename>", it turns out that I needed to use the format of "<packageprefix>_<modulename>". The package prefix is listed as the "Key" on the details page of the package in Admin area of SugarCRM.
This means that what I needed to input for the custom module name was "train_training" instead of "Training_Package_Training". Now that I've done that, I can access the custom SugarCRM Module.