You should read the manual about development for your platform, go to the opencpn.org website then follow the links to the manuals.

Then look at the plugins provided in the github source for OpenCPN. If you want to see how to build a complete plugin that does something then you can fork my testplugin_pi github.com repository.
This plugin is for developers who want to use the new ODAP in the ocpn_draw_pi. It shows how to call the code and is a working, simple, plugin.

Hello Friend.. I am from Argentina.. i see you know how develop plugins for opencpn, and I am interested in start to do something.. can you help me with some guide or simple program?.. I will appreciate that very much... Sorry by my English...