For linux server,
1. Connect to the ftp server via ftp client (ie. smartftp).
2. Select the files
3. Right-Hand Click and Select Properties/CHMOD
4. Set the permission as user requested.

There are three levels of file permissions: read, write and execute. In addition, there are three groups to which you can assign permissions: file owner, user group and everyone. The command chmod followed by three numbers is used to change permissions. The first number is the permission for the owner, the second for the group and the third for everyone.

Here are how the levels of permission translate:

0 = --- No permission
1 = --X Execute only
2 = -W- Write only
3 = -WX Write and execute
4 = R-- Read only
5 = R-X Read and execute
6 = RW- Read and write
7 = RWX Read, write and execute

It is preferred that the group always have permission of 0. This prevents other users on the server from browsing files via Telnet and FTP. Here are the most common file permissions used:

chmod 604 [filename] Minimum permissions for HTML file
chmod 705 [directory name] Minimum permissions for directories
chmod 755 [filename] Minimum permissions for scripts & programs
chmod 606 [filename] Permissions for data files used by scripts
chmod 703 [directory name] Write-only permissions for public FTP uploading