How can i customize our account statement ?

Welcome to the Community, @acc03-bsafesafet. Let me answer your question. 

There's few customization available for statements in QuickBooks Online (QBO). If you wish to customize your customer statement, I'll provide the steps below:

1. From the Gear icon, select Account and settings.
2. Choose Sales tab.
3. Click the pencil icon in the Statements section.
4. Turn on the Show ageing table at the bottom of statement. If you wish to see finance charges on your statements, choose List each transaction including all detail lines.
5. Select Save. Then, Done.

You can refer to this article for more information about customization: Create and send customer statements in QuickBooks Online.

But, if you're referring to something else, could you please provide more details so that I can give an appropriate answer and accurate steps.

Just incase you'll need to send physical or PDF copy of a statement or sales form to your customer, check out this guide: Download and save sales forms and statements in QuickBooks Online. 

We'll be keeping an eye to your reply for clarification about the statement you wish to customize or if you have other concerns within the program. Keep safe.