As part of the process to create a forum hosted at Nabble, an email is sent to the address you supply. That contains a link you need to click on to confirm you control that email address. Once you have done that you have access to your forum and can login in.
It is possible the email has been treated as Spam, so check your spam folder.
If the "Options" link does ot provide all you want to customise your forum then use the link "Edit this page". That will take you to a set of screens where you can edit the NAML code which controls your forum.
Volunteer Helper - but recommending that users move off the platform!
Once the admin for GregHelp now deleted.