Hi there, Shantilal.
Welcome to the QuickBooks Community. I'll be providing some information on how the template works in QuickBooks Online. This is to make sure that you can use it for your transactions and achieve what you want to view in your sales forms.
When you create templates in QuickBooks and you change the content of one invoice, it'll change everything. That said, you have the option to import a template for you to use on your transactions.
Importing your template allows you to have a more personalized to reflect your brand identity into your sales forms when emailing your entries. Please note that there are other areas in the template that will base on settings such as email set up and custom fields.
To start with, you’ll have to map the template fields. Please follow the steps below.
Once done, you'll have to save and upload your DOCX template in QuickBooks Online.
After that, you can click this article to see steps on how to finish the process: Import custom form styles for invoices or estimates.
Please refer to this article on how to automatically or manually send reminders to customers when their invoices are soon to be overdue: Send invoice reminders automatically or manually in QuickBooks Online.
Additionally, may I ask what do you want to perform next after importing or creating a new template in QuickBooks? I appreciate any further details so I can present accurate information.
If you have any other questions about importing a customize template, let me know by adding a comment below. I'm always here to help. Have a good one!