In order to become a member, you need to be a man over 18 (or 21 in some states), believe in a higher power, and be of good moral character. Your best bet is to contact the Grand Lodge of Florida as this site is run by the Grand Lodge of Massachusetts.
I can also tell you that there are several lodges that meet in Jacksonville, including:
Arlington Lodge
3421 University Blvd N
Jacksonville, FL 32277
Phone: (904) 744-0233
Duval Lodge #159, F&AM
2620 Dean Road
Jacksonville, Florida
32216-5137
904.737.1900
Temple Wesconnett Masonic (Masonic Lodge)
5917 Old Timuquana Rd
Jacksonville, FL 32210-7889
(904) 771-3759
Solomon Lodge #20
25 East First Street
Jacksonville, Florida
(904) 353-5263
There are probably others as well. Your best bet is to contact one or more of them and meet the different lodges to find out which you like best. Just contact them and tell them you are interested in learning more about Freemasonry and about their lodge, and I’m sure they’d be happy to help.
Best of luck,
Dan