The status of a Legal Permanent Resident can be acquired under the family, working and humanitarian visas contained in the Immigration and Nationality Act of 1952 as amended.
Based on the facts presented by you in your question, you are basing your legal right to become an alien lawfully admitted as a permanent resident on the relationship (brother) you have with an United States Citizen.
In order for you to acquire this status, your brother ( qualifying petitioner) must submit to the BCIS with jurisdiction over his place of residence a form I-130 Petition for Alien Relative.
Immigrant Visas are divided in Immediate Relative visas, and family preference visas. The relationship with your brother places you in the 4th level of family preference immigrant visas, and it normally places you in a long waiting period of time before there is a visa number available to you.
The Department of State publishes every month at no cost and open to the public through its website the "visa bulletin". The visa bulletin indicated the availability of a visa for beneficiaries with a pending application/petition depending the country of the beneficiarie's residence.
In order to start the process ( the sooner the better) your brother would have to prove the relationship existent between the two of you and this is accomplished by submitting a birth certificate of two of you indicating the name of your parents to establish conclusively your qualification under the fourth level of family preference.
Florida is a State that has requirements as to time of residency in the State as well as proof of legal immigration status.
If you are in the United States and you are looking to become a full time student, you must visit the prospective college campus you plan to attend and ask them what you need to produce in order to be enrolled.
Unlawful immigration status can be an obstacle to obtain the acceptance by a college, therefore you must inquire what the college you want to attend will demand from you.
This response is intended as a legal advise but at no time will constitute attorney client privilege or serve the basis as a negligence malpractice action. The legal advise is based on the facts presented in the question and are based on a general application of the Law as it exists.
A petition filed by a U.S. Citizen brother takes a long time. Currently, you may be looking at least 10 years depending on your country of birth. Immigration law is complicated and you would be better off retaining the services of an immigration attorney.
Your brother is not going to be able to petition you for the green card so that you can study in the US. The process simply takes decades.
J Charles Ferrari Eng & Nishimura 213.622.2255 The statement above is general in nature, as not all the facts are known. You should retain an attorney to review all the facts specific to your case in order to receive advise specific to your case. The statement above does not create an attorney/client relationship.