The easiest way is to install the following packages:
sudo apt-get install boinc-manager boinc-client
Then you can run the boinc-manager by running this from the terminal:
When it starts, you are first in the Simple View.
I suggest switching to the Advanced View, at least at the beginning to see the many options available.
You are initially prompted to choose a project. From the list, find and choose SETI@home.
You will then be prompted to supply an email address and password which is also used on the seti website to manage your account.
That’s it! Wait 10-15 minutes for the initial project to be assigned to you.
Below are some images of the many preferences available from the boinc manager: