Board Thread:Support Requests - Getting Started/@comment-44965987-20200409163639/@comment-9605025-20200409171015

Deleting files from the wiki can only be done by admins (and maybe content mods). If you are not an admin, you will need to ask one to delete it for you. If you are an admin, then you can delete the image the same way you would any other page. Go the the file page (for example, File:Example.png), click the edit drop-down, click "delete". In the future, you can simply upload a new version of the image to the same name. When you do this, the new image will overwrite the old one and update automatically wherever the old image was used.

As for removing from galleries, the gallery builder should provide an option to remove images. Hover over the image in the preview section. In the top right of the image, there should appear a "delete" option.