"World Community Grid is a simple way to support cutting-edge research into important global humanitarian causes. Your computer or mobile device could be powering scientific research on health, poverty and sustainability." 

I have been supporting World Community Grid since 2007. They have had many great causes come and go over that time. Currently, they are running work for cancer research, HIV/AIDS, microbiome immunities, Tuberculosis, and climate modeling for the African Rain Forest. The concept is really simple. Scientist that either don't have access to or don't have funding to run their calculations using a super computer will elect to use an alternative platform called Distributed Computing. What this means is that they will break down the work that needs ran into much smaller work units and they send them out to volunteers that run a piece of software that manages receiving the work units, "crunching them", and then returning these work units back to the scientists. You can configure this software to use your system in various different ways to your liking. The original intent of distributed computing through volunteers was to use the wasted CPU cycles of a computer sitting idle just eating electricity. Nowadays, entire teams of individuals are developing entire hobbies, communities, and even crypto currencies around distributed computing. 

To get started, you would need to download the BOINC (Berkeley Open Infrastructure for Network Computing) software. The software is open source. I recommend getting the latest version from the authors rather than from WCG. You can find that software here - https://boinc.berkeley.edu/download_all.php If you need guidance, there is a step by step in this forum thread for both Windows and Ubuntu - https://hardforum.com/threads/boinc-installation-walk-through.1768558/

After installing the BOINC software, you will need to tell it to connect to World Community Grid. The first time BOINC starts up after installing, it will attempt to do so. You can see the process in the link above. I recommend going to WCG's home page and setting up an account before attaching the client. Users have less trouble that way. Just go to here and sign up. Once your WCG account is set up, you can go back to the BOINC client and attach using the user credentials you just set up. From there, you will be running using the default settings. What confuses some people is that there is more than one place to make settings and preferences changes. The BOINC client just manages how the work units are used on the specific computer where as the settings at WCG's website tells the server how to provide work and some other general settings exclusive to just WCG. The reason for this is that you can actually support other projects with BOINC at the same time giving your resources to other scientists. 

There are a lot of terms to learn and many different ways to configure a computer to maximize its usage at distributed computing projects. All of them have their own needs as well as each sub project may as well. It is always good to ask questions in project forums or even team forums to learn the vast amount of ways to configure the host. Most just leave the default settings. However, if you are competitive you may want to seek out additional insight. My team can typically be found here - [H]ard|OCP and are always willing to help.