Like wa8yxm states there are 2 ways. blow lines or fill with antifreeze.
I fill my lines with antifreeze. I live where it gets below zero a LOT and for long periods of time which WILL freeze and break a line if you just blow out the lines and don't get every drop out of the lines. I don't like to take any chances.
I put the anti freeze directly in my fresh tank and pump it thru the whole system via the water pump. Been doing it for as long as I lived in Wisconsin. It's no different than pumping the anti freeze into the lines. The way I do it I 'know' I have antifreeze in the water pump.
De-winterizing fill tank with water open drain valve and drain the residue that might be on the bottom. Fill with fresh and drain again.
No problem. BTW it takes 10 times longer to get the smell and taste of chlorine out of the lines than it does antifreeze. :W