Cloudforge SVN supports locking by default - no special settings are needed.
To use it you will simply need to lock the file from your SVN client. All clients will do it slightly different. Here is how TortoiseSVN does it:
Locking a file ensures the developer who is working on the file, there will be no changes done by other developers who have access to the repository. However unlocking the locked files is also easy by following the steps in the below link: