Every user can now delete accounts themselves under User > Preferences.
For other account administrative help when working at usegalaxy.org, you can also send an email to email@example.com. The email should be sent from the same email address as the account is registered under.
If working at another public Galaxy server, the administrative contact information is usually on the server’s home page and/or at their directory listing here https://galaxyproject.org/use/. If you cannot find it, ask and we can try to help here. Please post the server’s base URL for context.
General usage questions should be asked at this forum. We will usually need the public Galaxy’s URL or a description of the private server (local, docker, cloud) you are working at for context eg: where sourced, version of Galaxy. The full name/version of the tool (if a tool question) also helps and will aid in community assistance.