Keep getting error: svn:can't get username or password when import project into repository

and the other problem it,after import it successfully in VP_UML,then perform checkout .keep getting:projectname already existed,…will delete current project…,I click:“yes” to delete current existed,then open project,nothing happened.
So can anybody give an instruction about:how to import current project into subversion repository,and late subversion to manage current project.Thanks.