There are a lot of naming variations for SPI (see list @ bottom), so the labeling doesn’t always match expectations, but they are labeled in the schematic
You need to use these 3 for the ? ones…CO is pico, 21 is CS, SCK is clock
Working on creating an easier pinout diagram for this.
Can you verify this Russell? I went by section 1.2.3. GPIO Functions (Bank 0) in the datasheet but maybe there are some specific changes for the ProMicro?