chances are then that it didn't get installed or it is in a directory not set in your search path (second one is pretty unlikely) You can search your system for it with this command
find / -name oowriter 2> /dev/null
on my system it is in /usr/bin so you may want to cd to that directory and check to see if it is there.
also you can use rpm to check the install rpms on your system with this command
rpm -qa | grep openoffice ( the | is the result of shift + \ keys)
here is what i get on my system.
[jeff@localhost jeff]$ rpm -qa | grep openoffice
openoffice.org-libs-1.1.3-9.4.0.fc2
openoffice.org-i18n-1.1.3-9.4.0.fc2
openoffice.org-1.1.3-9.4.0.fc2
by the last result i can tell it is installed on my system for sure. Once you figure out where it is this is how you make a desktop icon for it in GNOME
1. right click on the desktop
2. choose Create Launcher
3. in name field put "Open Office" (This is the name of the icon so make sure whatever it is you at least know it refers to Open Office - you could do word processor or something as well)
4. in command field type the full path of where the command is. so for oowriter on my system it would be /usr/bin/oowriter
5. in the box that says "No Icon" click and it will bring up a browser to pick the icon
good luck.
