Test between C & E with the DMM in "diode" position. using the red DMM lead for C, & the black one for E on an NPN transistor.
Reverse the connections for a PNP transistor.
Initially, it will be an infinity reading, or something else weird, indicating a very high resistance.
Spit on your finger & use it to connect B & C.
If the transistor is functional it should turn on, giving you a reading.
If it has very little effect, don't give up, as power O/P transistors don't always have a lot of gain, & a "spitty" finger might be too high in resistance to bias the transistor, on so use a 4700
resistor instead of the finger.
If you use an analog multimeter, note that most of them have reversed polarity on the Ohms ranges, compared to a DMM.
Your transistor is almost certainly a 2SC 6090 , which definitely is an NPN transistor, used in the horizontal output stages of analog TVs.