I acknowledge your interest in adding another user, ssaini. However, the option to add one in QuickBooks Self-Employed isn't available. Let's discuss this further below.
The Manage Users option is available in QuickBooks Online versions and you were watching videos related to it. While QBSE is primarily intended for solo use so this option isn't accessible. However, you can invite an accountant to your account.
I've added a screenshot below for your reference.

We can also check out this article on how to add to or remove your accountant in QuickBooks Self-Employed: Invite an accountant to review your books in QuickBooks Self-Employed.
Moreover, if you need to add additional users, you can consider switching to QuickBooks Online, which does support multiple users.
Refer to this article on how to transition from QuickBooks Self-Employed to QuickBooks Online: Switch from QuickBooks Self-Employed to QuickBooks Online.
Having multiple users work on the same financial data can enhance collaboration and efficiency. If you have any more questions about this topic, please leave a message here. We'll respond promptly.