Easy peasy. Snip the babies off at the end of the long stalk and either root them in water or soil/compost.
Water is the quickest way to get roots, and you simply submerge the bottom of the spider plant cutting for a few weeks. Make sure that the top of the baby is out of the water – use a narrow-necked bottle or create a bit of scaffolding on top of a jar for it to sit on. Alternatively, pop the cutting in some potting compost with good drainage.