As a Reseller, there are two (2) types of credentials you can create and provide. First, is a Reseller Employee Login. This type of Login is similar to the Login you have. They have access to all of the Accounts you handle, as well as each site under those accounts. Second, is a User Login. This Login is a restricted Login provided to End Users or Clients who wish to have access. These types of Logins may be restricted as you see fit; whether via the sites they can view or if they have the ability to make changes to the sites they have.
On the header marked Resellers, click the Plus + on the right.
Fill out the fields and press Save Changes.
Once you have an Account setup, you'll need to create a username to access the account. You can set permissions on each user from account admin to just viewer, and each account can have multiple users.
For adding a user to an account, please follow this Link
For Editing a user to an account, please follow this Link