Can I use Pioneer SP-52 speakers with my TX-8020 receiver? Do I need to do anything with the settings on the receiver?

I am very familiar with the Pioneer SP-FS52 speakers and think that your TX-8020 will be able to drive them.  Regarding the settings on the receiver, in your case if you are just connecting the one set of speakers I would leave the receiver set to its factory default setting of 6 ohms.  You would only need to set it to 4 ohms if you are connecting more than one set because the impedance would drop.