My preference is to get it from the Eclipse download site and then unpack it somewhere (I put mine at /opt/eclipse). I think it is also available from the package manager, but I usually prefer not to go that route.
I hope you know how to download the file - it's the same as on Windows.
To unpack, I assume you are using Gnome, in which case use the file browser to browse to the location where the file was downloaded, right click on the file and select the Unpack (or Unzip, or Extract) option.
Do you have a JVM?
Based on your questions here and some of your other forum posts, I recommend that you find some Ubuntu tutorials, or get a beginner's Ubuntu book to familiarize yourself with working on Linux.
OK, you did step 1. Now do step 2. I gave you the steps to use from a GUI, in Gnome it is the Extract Here option. You can also extract it from a terminal using the tar command. That is all there is to installing Eclipse.
You never said if you had a JVM.
It does not matter where you unpack it, but I put mine at /opt/eclipse. Of course, I first changed the ownership of /opt to my username. (I usually download files to my desktop, then using the file manager I move the downloaded file to the /opt directory, and unpack it from there.)