Debian packages for Regina are not distributed from the SourceForge site.
Instead, users of Etch (the Debian 4.0 stable release) may obtain packages from the repository on people.debian.org. These packages are available for the i386 and amd64 architectures. To install them:
Add Regina's location to your list of repositories.
This only needs to be done once (the first time you install Regina). Open the file /etc/apt/sources.list and add the following line:
deb http://people.debian.org/~bab/regina/ etch main
Update the list of available packages.
This lets your package manager know that a new version of Regina is available. How you do this depends on which package manager you use; an example for aptitude users is given below.
example$ aptitude update
Install or upgrade Regina like you would any other package.
Again how you do this depends on which package manager you use. Aptitude users might run the following command:
example$ aptitude install regina-normal
At this point your package manager should download and install Regina along with any necessary dependencies.
Regina is split into several packages for Debian. To start with you will probably just want the regina-normal package. If you are doing Python scripting and/or compiling Regina's mathematical core into your own code, you may want the regina-normal-dev and regina-normal-doc packages also. The regina-normal-mpi package is available for users running long census calculations on clusters.
You might have noticed that Etch already ships with Regina as part of its CD/DVD set. However, this is the older version 4.3.1 (which was current when Etch was released). For a newer version of Regina you should follow the steps outlined above.