The first step after purchasing subuser subscriptions is to go to the member area of the Pro user account where you will see a tab for Subusers - https://salesscripter.com/members/subusers. On this page you will be able to create the usernames and accounts for each subuser.
Here is the tricky detail - in order to find the new subuser in a search on page https://salesscripter.com/pro/crm/settings/organization that user will need to have to logged into their account at least once time in order for SalesScripter to actually activate the account so that they can be found in your search.
With that, after you create the subuser account, log into their account so that you enter into the SalesScripter application at least once. Then log back into your PRO account and perform the search for the subusers.