1. To fly for fun you don't need any permission unless you are flying in a restricted zone (around airports, military, etc) but there are some rules you need to obey like no higher than 400 feet, stay away from people, etc. mostly common sense stuff
2. To fly using Part 107 license for hire there are a lot of different restrictions like you can't fly at night, etc. and you will need to pass the part 107 knowledge test. (it's hard so study a lot and preferably buy an online ground school course like this one for $85
https://drone.flightready.net/remote-pilot-ground-school. You won't pass without a lot of study.
3. If your drone is locked out from take off you are likely in a restricted zone. If your close to an airport (typically 5 miles from tower) you need to call the tower and get permission. They will ask where you will be flying from, purpose, etc. Get the tower telephone number from airport website typically online.
4, Next go to
DJI - The World Leader in Camera Drones/Quadcopters for Aerial Photography and add the information they request, You will need the drone controller's serial #. The unlocking information will be added to a list in your controller and viewed from the settings menu. This will unlock your drone.