Assuming you are using OpenCPN for charts, your best source of info on downloading and installing charts as well as using all the other "bells and whistles" included in the program will be found at:
The OpenCPN WebsiteAs for charts, you have lots of choices including free, and not-free...
OpenCPN has a basic list of chart sources
hereFree download of NOAA raster charts for gulf of mexico and parts of the Caribbean basin
here and
here A set of charts for Cuba (converted from NGA's original format) are available
here.