I was served papers accusing me of contempt for violating a section of my custody order.

I have a court date in March. My question is that I cannot afford an attorney and will need to request the assistance of a public defender. Do I go to the courts now and request a public defender or do I do that on the date of my court hearing in March. I want to make sure I am very well prepared and just want to make sure I don't mess things up by waiting to request a public defender if I should be doing it now