Where shall I put this code for a top banner?

Hi @Sherran :wave: if you are just wanting to insert a banner image, the Vesatile banner component may not be ideal. Perhaps try having a look at this topic:

or have look at the various banner components in the theme-component category

https://meta.discourse.org/search?q=banner%20%23theme-component%20order%3Alatest_topic