What version are you using?
Do you mean that you can't get to the dev admin? Or that when logging into it, actions send you to the live admin?
In v1.3.9 and earlier, you would edit all defines for DIR_WS_CATALOG, DIR_WS_ADMIN, DIR_FS_CATALOG, DIR_FS_ADMIN and their HTTPS versions to include the web or file path to the dev installation. Also edit the DB and SQL defines to reflect the dev installation.