New villagers will not only build houses in the area and move in with their families, but also offer you their services. To use them, head to Achilles' place and use the Ledger which gives you three options: stockpile, crafting and trading.
Stockpile - this option lets you browse items which you possess and buy new goods from the villagers. The more of them you have, the more interesting items you can buy.
Crafting - it allows you to create new items from the materials that you have, which you can later on sell or use against the Templars. Items can be crafted in two ways: either by using a previously obtained pattern, or by experimenting with mixing craftsmen and resources. New patterns can be obtained in return for completing main and side missions. A list of both will be added to the guide later on.
Trading - this option can be used to trade goods by shipping them to shops. Firstly you need to choose the kind of convoy and items you want to ship and afterwards an interested party. Before making a final decision, you will be advised of the time of transport, risk of loss and anticipated benefits.