Set the multimeter to DC voltage
Select a voltage range higher than the battery’s rated voltage if needed
Connect the red probe to the battery’s positive terminal
Connect the black probe to the battery’s negative terminal
Read the voltage shown on the display
Compare the reading to the battery’s rated voltage
Check if the voltage is close to the expected value
Test under load if you want a more accurate condition check
Switch the multimeter to current or resistance only if required by the test
Remove the probes after testing