Here is how you can set permissions for whether or not your salesforce users should be able to activate customers via the "Send to Stax Bill" flow.
1. Search for "Installed Package" in the search setup bar and drill down into it
2. On the installed packages page, click Stax Bill.
3. On the Stax Bill package page, click View Components.
4. On the Package Components page, click the AllowActivationSetting setting.
6. On the AllowActivationSetting section, click Manage.
7. To set your organization default, click New. If you have previously set a default, click Edit.
8. On the AllowActivationSetting Edit page, select the default settings and click Save.
9. Now, you can set the settings for a specific User, if a user does not have specific settings chosen, then that user will default to the Organization level settings you chose above
10. Now select a User or a Profile and define what you would like the default settings to be.
11. You're done! The settings that you have chosen will be used in the following order
a. If a user has specific settings, then those will be used
b. If a user does not have specific settings, then it will check to see if that user's profile has specific settings, and those would be used
c. If a user's profile does not have specific settings, then the organization's default settings will be used