permissions on partition?

[Brian John]

Hello, I have a FAT partition on ad0s3 that I am sharing with Windows. 
For one reason or another everything on this partition is owned by
root:wheel.  I can't change the permissions to any files on this
partition.  This is what I have in devfs.conf:
own     ad0s3   brian:operator
perm    ad0s3   0660

Is this correct?  How can I make it so that files on this partition are
owned by the 'brian' user?

Thanks in advance

/Brian