Click on “My Learners” on the sidebar, and either add them individually (+Add) or add several learners at a time with the Upload button. Simply fill in their information, and select which Organization you'd like to add them to. You can also add training directly from here; when they create their account from your invitation, the training will automatically be added to their course list.
If you don't have an email or phone number (or if the information you have isn't up to date), you can send them the login token beside their name. They'll be able to fill in the correct contact information while still being connected to your organization.
Alternatively, you can click on “My Organizations” and click the gold “Add User” button. They will receive an email invitation to join your organization. They will need to sign up for their own account, either with their own email or phone number, but will still be a part of your organization once they join.