What kind of file extension is it? Natulius is designed to view folders, not run programs. I am a debian user, so rpm files are not my thing, but if it is an rpm, the command probably looks something lite this.
Code:
cd /(directory where the file is)
rpm -i filename
Like I said, I am not a Red-hat based user. You will have to check me on the syntax, but type that into the command line interface.