You will want to grab the unbranded page URL to i-frame into the website.
- Go to the board you wish to use and click on Manage
- In the board basic information window you will see buttons for the Public view and Public unbranded view
- Click on the public unbranded view and it will open a new tab in your browser that will not eliminate the navigation tabs. You will see the URL for this page. This is the URL you will use in your i-frame.