The Prozac should start kicking in and working to improve your anxiety symptoms within a few hours of taking the Prozac medication.
Then it can take a week or two weeks to fully see the results or feel the anxiety symptoms go away and stay away as long as you keep taking the Prozac anxiety medication as prescribed.
Don't stop taking the Prozac anxiety medication unless directed by the doctor first otherwise it could cause problems when you simply stop taking the Prozac anxiety medication.