Before asking a question on the Oomph Discussions, please read the general instructions for how to use the eclipse installer. While it's true that there's no such thing as a stupid question, good answers nevertheless depend on the quality of the question. Help us help you by providing details.
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Where Should I Install?
Eclipse installations are generally designed for personal use and are self-updating. As such, you should typically install to a location for which you personally have write access. This is why the default location for the installation is in your home folder.
While it is possible to use the eclipse installer to create a so-called shared, read-only installation, you should read carefully the additional considerations below. In particular, it's important to either disable the use of the shared bundle pool, or to ensure that the shared bundle pool is also located in a read-only location that is accessible to all users.
How is my Network Used?
If you are behind a network proxy, you will likely need to configure your network connections first. The eclipse installer will automatically open a dialog for these settings if the catalog fails to load.
The eclipse installer relies heavily on the network to load the latest catalog and to fetch information and artifacts from various p2 update sites. Unfortunately many things can go wrong with the network between you and the servers providing this data. It is not entirely a rare occurrence that the download.eclipse.org server itself becomes over loaded. To avoid this, installation artifacts will typically be downloaded from so-called mirror sites; unfortunately the servers for these sites too can fail for various reasons. If you experience a network failure, please try again a short while later.
What Else Should I Consider?
By default the eclipse installer uses a shared bundle pool to reuse installation artifacts across multiple installations. This has the advantage of making each individual installation very small so that you can easily and quickly create many specialized installations for different use cases with minimal network traffic and minimal disk footprint.
Use the eclipse installer's Bundle Pools... menu item to manage where this pool is physically located on disk; this location can become large. The Bundle Pool Management dialog supports garbage collecting of unused artifacts, i.e., if you delete an installation, the artifacts it uses can potentially be removed from disk. In addition, if some artifact becomes corrupted, or if a corrupted artifact is downloaded from some mirror site, this dialog can be used to detect the damage and to repair it.
Can't I Just a Download a Package?
If the eclipse installer fails to serve its purpose, you can always download a pre-packaged installation as an alternative.