Unlike DOS, UNIX has no concept of drive letters. To understand it, let's look at a small directory listing as made with the ls -l command. The permissions are indicated by a series of rwx's on the left side of the listing. The first position indicates the type of file. The remaining nine characters indicate the permissions given to the owner, group, and others.
X means execute permission- except for directories where it means search permission.
Usually these are not in your web directory. Check the help file with your FTP program for the exact instructions. The most popular UNIX editor. Can be found on every system. Here is an excellent Quick tutorial by Tony Thomas.