To generate a statement for an account, you first need to expose the Statement button in the Account layout.

Go to Setup | Object Manager | Account | Page Layouts. Edit the desired layout (i.e. Account Layout). Under Mobile & Lightning Actions, drag Statement to the Salesforce Mobile and Lightning Experience Actions section: 

In Classic View, drag Statement from Buttons under Custom Buttons section.

To generate a statement, go to the account details page and click Statement. The following page will be displayed: 

With the above page, you can:

• Select a date range for the statement

• If you are using multi-currency, select the currency of invoices and payments you wish to display

• Email the statement

• Print and Download the statement

• You can also edit certain portions of the statement to match your branding. Simply click the Edit Template link and that will lead you to the editor. Note that this requires some knowledge of Email Templates.

This feature is available in the Sep 2013 release.