If I remember correctly, OpenOffice installs from a binary file. If you want to run the file (and you do) go to the directory it's in and do: ./the-name-of-the-file (that's dot slash file-name).
If the file won't run, then do: chmod +x the-name-of-the-file (while you're in the folder containing the file)
That applies to any shell script (.sh), or binary files (.bin) (the .sh or .bin extensions aren't always there, though).
If I'm wrong about OpenOffice and it it comes as an RPM file (.rpm) then do: rpm -Uvh the-name-of-the-file.
As for the multi-user thing, you can set which users can run and see which files (and therefore programs) using user groups and assigning a group access to each file, again with chmod (type in man chmod at the command line for more info) or you can do this in KDE/Gnome etc.
If just want certain users to not have KDE or Gnome entries for certain programs then you can edit the files which contain the menu entries.
Here's a sort of guide for KDE (it says where the files are held, and how to make new menu entries ):
I don't know about Gnome though.
Hope this helps.