Long long ago, they didn't have the
edible synthetic tubing to make these sausages - you had to clean out the
small intestine of the pig to get your tube. Of course, it also tasted better then!
To cook them while cooking steamed rice: slice the lap cheong into thin slices - cutting them at an angle will maximise surface area - and place in a metallic plate with some light soya sauce. Place the place into the electric rice cooker when the steam is beginning to rise vertically from the cooker, or the equivalent if you have a clear-lid rice cooker, when most of the water has evaporated from the rice leaving "dimples" in it. Leave to cook. Serve when the rice cooker tells you the rice is cooked (or you might just want to wait a few minutes just to be very very sure).
This obviously assumes you have a rice cooker - well, Option B assumes you have a microwave oven.
Place the sliced lap cheong into a microwaveable plate with some light soya sauce. Power setting on HIGH for about 40 seconds will do it for you. Of course, it depends on how thinly you slice them.
Other ways to have lap cheong : in fried rice, as part of a stuffing with glutinous rice inside a duck or dumpling (loh mai fan).