What is the process for processing salt water into drinking water?

The process that turns sea water into drinking water is called "Desalination of Sea water". There are several technologies that do this. The most popular and economical today is a process named "reverse osmosis".

In Nature, formation of clouds by evaporation of sea water, its condensation to form clouds and raining it on the land gives us plenty of drinking water in unpolluted streams and rivers.