I worked at a distance learning college for adults, Thomas Edison State College, before I retired. Hundreds, if not thousands, of my students took the CLEP General and/or Subject exams.
The five CLEP general exams are English Composition, Humanities, Social Sciences, Natural Sciences, and Mathematics. You can take up to four of them on the same day. They are worth six credits each at colleges that accept them (community colleges almost always accept them; only some universities do) at full credit. Thus, if you have no other college credit, you can earn a full year of freshman-type credit. Or you can decide that three of the exams appeal to you and skip the others. There are many books on preparing for these exams - pick one up and work thru it. They give both study material and sample questions. When you can answer the questions you are ready to take the exams.
There are many subject exams - around 30 or so in specific college courses, such as College Algebra, American Literature, or Macroeconomics. For these get a standard college textbook and work thru it - it helps if you already know some of the material in the course.
If you like, I can PM you my phone number and we can talk. I advised adult students for 25 years.