The MPRE (Multistate Professional Responsibility Examination) consists of 60 multiple choice questions. Each question has four possible answers. You have two hours to complete the test. Florida requires a scaled score of 80 for a passing grade.
Most importantly, the test is administered separately from the rest of the Bar exam and can be taken prior to the Bar. It is given three times during the year, usually in mid-March, mid-August, and mid-November. Various test locations are offered in Florida.
For registration, fee information, and deadlines view the NCBE page here.
Florida requires that an MPRE passing score be attained within 25 months of passing the other portions of the Bar examination.
Also, Florida allows you to take the MPRE prior to graduation from law school. Given that the test covers the national ABA Model Rules of Professional and Judicial Conduct, it is recommended that you complete Professional Responsibility (LAW 6750) prior to sitting for the exam. Since the course is required and a pre-requisite for various other electives, some students take Professional Responsibility early in the 2L year.
Most students take the MPRE as a 3L. Some give themselves enough time to take the test for a second time prior to graduation, in case of a 'fail' on their first try.
You'll need to set up accounts with the NCBE first and then with the LSAC if you haven't already done so.
The MPRE's subject matter outline can be viewed here.