CHMOD, which stands for "CHange MODe" is a way to change file permissions on Linux, Unix, and similar servers. Most servers run one of those two, but some run Windows - in most cases, if your server is running Windows, you will have to contact your host to get permissions changed. If you're not sure, it can't hurt to try ;).
Most FTP programs allow fairly easy access to this, such as Filezilla (http://sourceforge.net/projects/filezilla), SmartFTP (http://www.smartftp.com/), and others. To change a file or folder's "mode" or permissions, simply right click on it and go to "permissions", "properties", or "chmod". Some clients will instead have a button to press, or will require Ctrl-click (Mac.)
Please see the below screenshots:
Read more (http://www.google.com/search?hl=fi&q=chmod+tutorial&btnG=Hae&meta=)
For BulletProof FTP (similar general appearance):
Select directory and/or file (remember Ctrl and Shift can be used for multiple selections), right-click, select Change attributes and either check the boxes or type the number.