Do you have the right to change filepermissions on the file you are trying to change? Probably not. Do an ls -l to see the filepermissions. You read left to right: Owners permissions (the one who created the file), Group permissions and then the others permissions.
So, you might see something like this:
-rw-r--r-- 1 erik users 128 Jun 6 2000 welcome.msg
Wich means, erik (the owner) has read and write permission to this file. The group users have the right to read the document, and the others have allso read permissions.
To illustrate: 'chmod o+r filename' give others (everyone) read permissions. 'chmod g-r filename' remove read permissions for the group, and finally 'chmod u+rwx filename' give the owner the right to read, write and execute the file. The operators + and - adds or takes away a permission. You can allso use = to make it the only setting. Say 'chmod u=rw,g=r filename' which would mean the setting will be user have rw and group has r and other have nothing, no matter what the rights where before the change
So when BSD check to see if you have right to change, it first look, are you the owner for read and write permission? No. Then are you in the group for read permission? No. So does anyone that doesn't match these other permissions have the right to do anything with the file? Yes, everyone is allowed to read it. Then it shows it to you.
Now, your file might have something like -rw-r----- and you don't own the file or are in the group to which the file belongs to. Then you are not allowed to change it (even if you are in the group you wouldn't get to change it scince you would still only have read permissions)
Now, this chmod business (related commands: chown, chgrp) are the same on all unix systems, and as Bob Loblaw you can allso use numbers to set permissions. So do a search on altavista or whatever for chmod and you will find explinations on how to do all of this.
After this throughout explination, I hope you have no more questions about chmod though
Oh, I almost forgot. To change to superuser you just use su. I assume it's the same as on OpenBSD in which case you would need to add yourself to the wheelgroup to do this. Just login as root and edit /etc/groups and add username to the wheelgroup. Then logout and use su instead of logging in as root in the future!
Type su and enter, it will ask for a password, give it your root pass and you are in as root. Now, when you are done just type exit to ascape to normal user.
An even better solution would be to use sudo. This let you give a command as root without logging in as root (as you do with su).
Don't know if this comes with FreeBSD, but if it don't it should be somewhere in the ports tree. Install it, read the manual, it has the instructions you need to know and you should be on your way.