OP, you can file it.
Just take it down to the Courthouse, go to the filing clerk's office and file it.
It has to be signed by you requesting the change, your attorney agreeing to the withdrawal, and by you again as the new attorney if you are representing yourself (or the new attorney if you are represented).
If you have a trial pending, the Judge may not allow a change of attorney, or may not allow any continuances because of your being unprepared to proceed.
Take three copies to the filing window. Get a file-stamped copy from the clerk.
You also have to serve this on opposing counsel or your spouse if she is representing herself.