If you don't have the hose and valve by your pump, as suggested earlier, you can use a hand pump. It is available at RV shops and sometimes Walmart. It attaches to your city water in and the other end in the gallon of antifreeze. It looks like a bicycle pump. Pump away and open the faucets starting with the closest. It doesn't take long, but you will need an extra hand in the camper to open and close the faucets. Don't forget p traps, toilet and outside shower. It will save a lot of the pink stuff. I also put a gallon or two of windshield washer fluid in the grey and black tanks, so they don't dry out. It's good down to -50 and cheaper.
You can also blow the lines out with air. They make an adapter that goes on your water hose connection. Put a air compressor on it and open the faucets like the antifreeze method, an extra hand comes in handy here too. When by myself, I open a faucet before putting in the air, then go inside and close and open the faucets till water stops coming out. I leave the last faucet open, till I turn the pump off, then close it. If you put to much air in you might blow a line. My little pump has to go like h.. to do that though, but I still don't take the chance.
I do both. The air first then the antifreeze. I open my low point drains and save the pink stuff. Might be overkill, but it's my trailer and my time. I'd just be watching TV anyway.