unpack the archive with
tar xfvz filename.tar.gz
it will create a directory under your current directory, change to this directory with
cd newly_creted_directory
and look for a README, INSTALL files for further instructions.
P.S. everything stated assumed you are working in an Xterm/Konsole/tty/other terminals
Or better solution is go to
http://www.openoffice.org/dev_docs/instructions.html and volia!