If your PC is connected to the Internet, there’s nothing stopping you from beginning to fold immediately. Point your browser at https://foldingathome.org/#downloads and choose your operating system. From there, install the client, and set up an account. Perhaps join a team, which pools the research carried out by multiple donors and turns it into a kind of competition between teams as to who can process the most work units. There’s a Maximum PC team, naturally: number 11108.
The minimum specs are very low, in the Pentium 4 and Windows XP range, but the more cores you can give it, the happier it will be, and only a limited number of projects are available for 32-bit systems. Once connected, you’ll find the client lurking in your system tray.
There are two control panels: Web Control, which runs in the browser, and gives you a basic overview of what Folding is doing with your system; and Advanced, which is its own app, and gives you more detail and more control. You can pause the process, set how much of your system’s resources you want it to use, and whether you want it to use both your CPU and GPU (multiple GPU owners can add a second GPU slot, and potentially process three work units in parallel). You can also set it to only work when your PC is idle, leaving all the power for you when you want to work.
We had to turn the “Power” setting down to “Medium” on our AMD Threadripper/Nvidia RTX machine, simply because the heat it was generating from running fulltilt was making it uncomfortable to work in our office. Watch out also for clashes between Folding and your antivirus software—if this happens, exclude the “Folding” folder from your antivirus scanning list.