find ~ -name apt.no looks for a file or directory*
apt.no in your
$HOME directory and within any directories underneath it. (The
~ represents your own home directory.)
montrose-files is within your own home directory it won't be searched, and the target file won't be found. For example, if
montrose-files is under another path, you'd need to specify that path:
find /path/to/montrose-files -name 'apt.no' -print
Confusingly, if you have previously created a symbolic link to
montrose-files in your home directory that also won't be searched, as
find by default does not follow symbolic links. You can address that in one of two ways:
find ~ -follow -name 'apt.no' -print
find ~/montrose-files/ -name 'apt.no' -print
In the first approach we tell
follow symbolic links. With some versions of
find this can be a poor approach, because if a symbolic link points around in a loop you could end up traversing the structure several times.
In the second approach we force the symbolic link to resolve to a real directory target by appending a trailing slash.
Finally, notice that in all cases I've quoted the filename for which I'm searching. In your simple case it won't make any difference, but when you start using wildcards to match unknown parts of filenames (for example,
apt.*) you should use the single quotes to ensure the wildcards are not processed by the shell before
find can get hold of them). It's a good idea to get in the habit of quoting arguments.
* Technically, it will match any item at all, but you're unlikely to have pipes, sockets, or device nodes in your home directory