GPS guided boat movement

I'm currently working on a project wherein the boat would travel on fixed paths with the aid of a gps module. I could now get the NMEA sentences and parse it to separate the longitude and latitude of location of the boat. I'm now working on creating somewhat like waypoints for the boat.

Although the problem is that I don't know how to utilize the coordinates given by the module to move the boat to its desired location.

the problem is that I don't know how to utilize the coordinates given by the module to move the boat to its desired location.

You know (roughly) where the boat is.
You know where you want the boat to be.

If the distances are not too great and there are no obstacles in the way, 2D trigonometry should give you the heading, and from there, it's a question of minimising the error between your current heading and the desired heading, which is continuously recalculated as you go.