Thanks for joining the growing family of QuickBooks Community, Daisy21.

 I'll be delighted to guide you in locating the Customers tab. Please follow the steps below:

     1.Log in to your account.

     2.From the top menu, select Customers.

Take a look at my screenshot below:

From there, you can create estimates, sales orders, and invoices to your customers. 

Please tag my name in the comment section if you have any further questions or concerns . The Community always has your back.