Impact uses the Salesforce security model. This will ensure only the users that you have granted access to Impact will have access. We do this by taking advantage of Salesforce Permission Sets. Simply add the 'Impact Learner' Permission Set to your Salesforce Profile and you will automatically grant all the security access necessary to use the application.
We also use Salesforce for Single Sign-On, so that there is no need to re-create new users, simply leverage the Salesforce users you already have.
Impact also has Course level security. This will allow you to share your courses with the people you want to have access. We have two ways to share courses. First, you can share courses though a Group Library, and allow for mass sharing and access. Second, you can share the course at an individual level for a smaller distribution of material.