Doing my first upgrade on a pre built (2nd SSD)

I’m new to PCs in general and I’m about to do my first little upgrade on my pre built. I am adding a second SSD and it’s an upgrade over the one it came with by a mile. I would like to make it my main SSD. I understand how to add it and to get it installed and that I need to clone it. After I do that (or before ) should I switch the new one to the m1 place and other to the m2 ( hope I’m labeling those correct ) or does it not matter ? I also know I’ll need to go to BIOS to choose my boot drive as well.