Hello info145.
Statement templates run from the Master invoice template, so you will need to add you bank details to that. Go to the cog wheel, custom form styles and click 'edit' next to the template which is marked as 'Master' under the form type header. Once on this template, click content and select the bottom section of the invoice. Here you will find a box to enter your bank details, once you have saved this, it should appear on your statements.
Thanks,
Talia