To start working with files in your newly-cloned repository, your best bet is just to "check out" every single file throughout the entire repo (if they aren't already). You can be selective about what to check out but, for now, you might as well just get everything.

From the root of your cloned repo, this command will check out (with read-only permissions) everything recursively:

 $ bk -r co -q

Please note that the NTP project has its repos set up to automatically check out all of the files in the repo in edit mode (with read-write permissions).