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Table 1 on page 6 of the user manual provides the symbol for capacitance. Page 8 shows the input terminals to use for capacitance. Page 19 describes how to measure capacitance.
I would lay the test leads flat on a table or whatever and spaced apart with clips near the end of the cable and take a reading. Make sure the cartridge is disconnected. Then carefully clip the leads to the cable (plus to center pin, minus to shield) without moving the leads and measure again. The difference is the cable capacitance.
You cannot hold them with your fingers as that would add too much capacitance and be highly variable.
The issue with using an inexpensive multimeter for this is that the capacitance range and resolution are too high to be very accurate for measuring cables. On the lowest range, that meter has 50 nF max reading and 0.01 nF (10 pF) resolution, plus the error band. Typically cables run around 20~30 pF/foot (RG-6, commonly used for TV and audio interconnects, is around 21 pF/ft) so you are measuring in the very lowest part of the meter's range. These meters are mainly to check large power supply decoupling capacitors and larger interstage coupling capacitors.
Most tonearms provide the capacitance of the cable to the connectors. You can look up the capacitance of the interconnect if you know or can figure out the type of cable. But frankly I would estimate the length in feet from cartridge to preamp and multiply by 25 pF/ft for a rough idea (25 because the tonearm wiring itself tends to have higher capacitance than the interconnecting cable and phono interconnects are often smaller and more flexible with higher capacitance).
At one time I used some low-capacitance cable (RG-79, ~10 pF/ft) to connect my TT to my preamp but that tends to be big (~0.5" diameter) and harder to handle.
I use an RLC meter or VNA but those are expensive options I borrow from work. At home, long ago when I had a TT set up, I would play a test record and measure the frequency response after the preamp, adjusting the capacitance for a flat response. That measures after the RIAA compensation and all that jazz but was easier to do with tools at hand.