There are only a few reasons for changing out the drain pipes under a kitchen sink. The most common is during a kitchen renovation when the sink is being replaced. The steps for how to install a sink drain will depend on how different the new sink is from the old one as well as what other components are being installed. In older homes the sink is not likely to be as deep as they are now so retrofitting may be necessary.
Here is how to install a sink drain from start to finish.