Where do you live? Captain license to operate as a paid captain or privately? Do you really expect intelligent answers to such a vague question?
Not familiar with the licensing authority in Dubai, but that's who you should ask. Here in the US, our Coast Guard is our licensing authority... and there are several levels of licensing. The least expensive, often appropriate for a 27-footer, is to become an Operater of an Uninspected Vessel (OUPV) for up to 6 paying passengers (hence the nickname "6-pack"). There are several ways to qualify -- once having accrued the minimum required sea time -- but the least expensive is to just study their material and take the test. That's just an example, but perhaps your licensing authority has something similar. Or maybe you're just asking about how to attain an operator's permit or certificate, something that indicates you might not kill yourself or somebody else on your first trip, perhaps required by your government? We wouldn't normally call that a "license" here, but the answer is likely similar: check with your maritime authorities. -Chris
In Dubai, you need to go to the DMCA (Dubai Marine City Authority) office in Al Barsha, they'll explain you your options. If I recall correctly there was 2-3 different types of licenses depending on the length of your vessel.
If you are in Dubai, contact Marine Concept, the IYT yacht training sea school. They will assist you with your requirements. http://www.marine-charter-concept.com/en/sea-school/iyt-training-courses-certificates/
If this topic is not yet close, you can consider taking RYA course. Here in Dubai, you have IYT & RYA. Both institute gives you training and certificate for you to proceed with the next application which is to DMCA.
And ... Study the Rules of the Road every day until you take your test .. and then review them at least monthly.
You could probably ask the port authority in the are where your boat is registered. From what I know if you have a respected license you can dock in lots of countries ports. You might have to multiple licenses if you want to dock everywhere.