You can prime it. Make sure the lid seals.
Making sure the lid is sealed, that's probably the trickiest part.
This is what I would do:
- Presuming the keg is "full," leaving about 1 pint to 1 quart of headspace.
- Add the correct amount of your (dissolved) priming sugar for the CO2 volume you want to serve at, and lock the lid.
- First purge, then pressurize the keg's headspace with CO2 from your tank to about 15 psi, to set/seal the lid.
- Test the lid's seal/perimeter for any leaks (bubbles) around the edges using Starsan, soapy water, or bubble juice.
Put the keg in a 60-66F environment to carb up over 2-3 weeks.
Then place the keg in the kegerator/keezer, but
do not connect any lines to the keg yet. Give it 2-3 extra days so the keg is thoroughly cold, and allowing for the pressure/carbonation to stabilize.
Then vent off some of the (extra) pressure by pulling the PRV valve.
Use this calculator to set the gas pressure according to the volumes you want to dispense at:
https://www.hopsteiner.com/psi-calculator/
For example:
for 3 volumes at 36F, you'll need to set the regulator at 15.3 psi.
for 3.5 volumes at 36F, you'll need to set it at 20.3 psi.
Only after you've set the regulator at the corresponding pressure you want, flush the gas line with CO2 (press the poppet in the QD), and connect it to the keg.
To serve at higher pressures (say over 10-12 psi), you'll need longer and/or skinnier beer lines:
http://www.mikesoltys.com/2012/09/17/determining-proper-hose-length-for-your-kegerator/
I'd recommend using EVA Barrier lines for both beer
and gas, as they have an
oxygen barrier, preventing your beer from slowly oxidizing while it sits in your kegerator.
They come in 4, 5 and 8 mm ID. For example:
https://www.brewhardware.com/product_p/evabarriertubing4mm55.htmThat also means you should get the corresponding push-to-connect fittings.
The 4mm ID beer line will give you much of the needed restriction when using the higher serving pressures associated with a beer's higher carbonation levels. Everything needs to be in balance or you'll have much foam and little beer that's halfway decarbonated.
You could use 5mm, to pour faster, but you'll need much longer beer lines.
Of course the gas lines are not affected, they can be as long or short as you see fit. Pun intended!