To trade all you need to do is build a port, then a trade post. Then connect your port with ships in every sea province with another port controlled by another faction. Just repeat this process untill you have all the nations you want to trade with, or be like me and spam all the sea provinces next to the land with ships. Soon you will start to see a huge inflow of money.

Also since you game didn't come with a manuel it would be very ideal if you checked out frogbeastegg's excellent MTW guide located here The Guide

Hope this answers your question and welcome.