Find someone qualified and willing to administer an IQ test for you. Try using a search engine for something like "where to take an IQ test," with the name of the city closest to you. If you can't find a nearby location, Mensa administers IQ tests on a regular basis, and you can find the closest branch on its website (listed in the References section).
Take the test. Get a good sleep the night before the test and make sure to eat well and drink adequate water. Besides that, there is little that can be done to prepare for an IQ test, though Mensa has a fun workout on its website to get you in the IQ-test mood.
Wait for your score. The test will have to be scored, and probably won't be available to you directly after the test. Depending on the organization you take the test with, your score will probably be mailed to you.
Apply to high-intelligence societies such as Mensa if your score is adequate. If nothing else, membership will look impressive on your resume.