I'd like to officially welcome you here as a new user. There's definitely a lot to learn when starting with QuickBooks, smaribha.
Adding clients in QuickBooks Online Accountant would automatically show up in both the Customers and Clients menus. However, the system will show clients who are marked as having a subscription by default.
Follow these steps to see all your clients:
- Go to the Client list tab.
- Click the dropdown menus for both Client type and Lead accountant, and select All for both.

You can also check out this article for more details: Manage clients in QuickBooks Online Accountant.
The Community is always here if you need anything else.