Open the back of the sausage machine and push in as much of the salami mixture as will fit. Reattach the handle, then wind slowly until the mixture fills the nozzle and just reaches the tip (this will prevent an air pocket forming inside the casing). Remove one of the casings from the water, squeeze out as much water as possible, then slide it onto the nozzle, pushing it back until just 2.5-5cm of casing is hanging off the end. Tie a knot on this end to seal using twine or butcher’s string. While holding the casing in place (this is easier with two people), begin to wind the machine slowly, so that the mixture starts to fill the casing.