We don't support 3rd party images - ask the author of the image for support. Otherwise, if you'd like to start from scratch - you can see in the docs how you can install a new image and, yes, it will overwrite everything you have on the card.
Contributions to the project are always appreciated, so if you would like to support us with a donation you can do so here.
Hosting provided by Mythic-Beasts. See the Hosting Information page for more information.