Basecamp users please refer to How do I add Basecamp users or resources?. To bulk import multiple resources from a spreadsheet go here.

Important: Roadmap distinguishes between users and resources:  Users can login and be assigned to things, whereas Resources cannot login but can still be assigned to things.

To add an individual user or resource, click the "+" in the upper-right corner (A).

After adding resources or users, go to the Resources Tab and select All Resources view to make further configurations.

• Type (B) indicates whether it is a user (icon has color), resource (icon is gray), and further distinguishes resources by whether or not they are a person or a company.  Clicking a resource icon allows you to migrate them to a user with a login.  You can also downgrade users to resources using the Type column.
• Assignable (C) indicates whether the user / resource is available to be assigned in any of the responsible party dropdown menus.  You may want to mark a user / resource as not assignable if they are, for example, on extended leave, or if they are a user like a senior manager who is unlikely to ever be assigned to things.
• Primary Project Role (D)
• User Access Groups (E) allow you to create project-level security and permissions
• Schedule (F) allows you to define a user / resource as full or part-time