The PSAT/NMSQT will be administered on October 16 and October 19 to high school juniors. The PSAT is a "practice" test for the SAT and colleges do not see scores. So there is no need to prep for the test. But it can provide important feedback about where you need improvement.
Also, scores on the PSAT taken in the junior year are used to qualify students for the National Merit Scholarship competition, the best- known scholarship program in the country. So a strong score could translate into scholarship money.