A Free Colonist working as a trapper on a forest tile may spontaneously learn to be an Expert Fur Trapper after some time.
The New World is abundantly supplied with fur-bearing mammals whose pelts can be sold for a handsome profit in Europe. Native Americans have long studied and trapped these creatures for their fur and meat. Your people can learn the ways of the forest creatures and become master trappers only from the Indians.
The best place to find fur is in wooded country, especially in colder climates.