To answer your question, you register for the exam on this site: https://www.ets.org/praxis.
I've taken the English exam (Praxis 5038). If you do the free practice test that comes with registration, you should be alright. I also got this book that did a great job of going over the material. If you Google "Praxis 5038 test prep," you may find some resources from others as well.
A lot of Praxis exams can be taken at home if that's something that interests you. Let me know if you have any other questions!