If you would like to add a button labeled Give Now to your website, so that people can access your Give Now interface from Vanco, you will need either a picture of a button or the code to display a button and a link from Vanco that is linked to that image or included in your code.
Insert the image on your website and then use the WYSIWYG (edit page) editor and click on that image. Then click the chain link, from the toolbar that's activated, and paste in the link from Vanco. Also, set the option for New Target, so that the link opens in a new browser tab.
<a class="btn" target="_blank" href="your link here">Give Now</a>
Note: this should be inserted into your code where you would the button to show on your page