In Qmarkets, there is the option for external users to self-registate to the system.
Read this article to lean more.
In case that admin approval is needed, once a user registered to the system, he/she is being notified on the next steps:
The user sees an on-screen notification, and gets an email saying their information needs to be verified by a moderator/Admin.
This is an example for the email that is sent once the user registers:

Once the admin will approve the user's registration, a 2nd email will be sent to this user notifying him/her that he/she can start using the system.
The approval request mail is sent to mail address specified in the site information page.
This email address is provided by the customer and inserted by Qmarkets Admin as part as the IT onboarding process.
It is important to choose a true & valid email address that will be monitored by the system admins.
In case the approval can be done by multiple users, the email address can be a mailing list.