Subversion will only work with local files that are a valid working copy of the files from the Subversion repository.
In a nutshell, this means the local working folder must contain a set of files that at one stage was checked out of the Subversion repository.
If the project was imported using Agent SVN that process will automatically create a working copy.
Alternatively, Agent SVN also support the Check Out From Source Control option, so if your IDE supports this feature, that approach will also create a new folder containing a valid working copy.
Finally, another way to create a valid working copy is using a tool like Tortoise SVN and use the check out option.
If the following dialog is displayed then it means the project's local folder does not contain a valid working copy.