I'm afraid I can't do much but give you general pointers. I tried to download the RealPlayer 10 installer for FC 4, but the installer wants an older version of the standard C++ library. Anyway...
When you ran the RealPlayer 10 binary file you downloaded, it probably extracted a number of files. One of those files is likely named "realplay." The installer might have mentioned or asked where you wanted to install RealPlayer to. I'd check that directory for the script. If you have no clue where to even start, do this:
find / -iname "realplay"
That might take a while, but it should tell you where the script is on your machine, if it's present at all.
Once you find it, do like the instructions say, and make a symbolic link to it in a directory included in your PATH environment variable. You'll likely make the symbolic link in /usr/local/bin, but that's not a rule or anything.