Click on the little wrench icon at the top of the screen
in OpenCPN. Choose the "charts" tab and add the directory that contains your existing charts. Odds are they'll work.
If not, read about the usable chart formats here: Chart Formats | Official OpenCPN Homepage
. There are lots of options.
If you're interested, you could join our group effort to convert the NGA charts that are currently available for viewing online into usable .kap files. Search in Cruiser's Forum for "NGA charts" and you'll find a long discussion thread that gives the background of the project
The NGA charts themselves are at OpenCPN.info (English)
. If you choose to join the group, most of the Caribbean charts are already available. But be aware that these are still very much in an Alpha test phase and have not been fully checked for accuracy. Since you have complete coverage in paper charts and seem to be a careful navigator, you might be a good Alpha tester.
Also, the CM93 charts that are floating around on cd's amongst cruisers cover your part of the world in detail and work fine with OpenCPN. Ask around the anchorage or marina, and you'll probably find someone who has a copy they're willing to share.
Also, search in Cruisers's Forum for GE2KAP and you'll find a thread about a utility that can convert Google Earth
views into usable charts in Open CPN
. There is a link to the utility on the page I linked above. These would be quite handy as a supplement in many parts
of the Caribbean.