If you want to enable one of your end customers to self-service their licenses, you need to:
To enable self-service for one of your end customers, in SpinPanel, open Settings > Relationship settings. From the Relationship drop-down list, select the end customer for whom you want to enable self-servicing, then click on SpinPanel settings and then click the Edit-button. Switch the option Self-service to on.
After you enabled self-service, you also need to assign a role to at least one user with your end customer, giving that user sufficient permissions to assign licenses. You can create a role that will only give permissions for license management.
To create a role, in the SpinPanel side menu, open Settings > Role management. As the role needs to be created for your end customer's organisation, make sure your end customer is selected inside the organisation drop-down in the top right hand corner.
Inside the Role management page, click the Add-button. Inside the New role side-pane, fill in a value for Role name, e.g. "License management", switch on the License management toggle and click the Save-button. Turning on this switch ensures that all permissions required for license management are turned on for the role.
Once you've created a role with sufficient permissions for license management, you must assign this role to one or more users of your end customer.
For more information on assigning a role to a user, please read this article.