Start to build your game using your designs to help you.
Use a development log to record:
Create a development log. You should update it regularly during development.
Test each part of your game as you develop it.
Ask game testers to play a prototype of your game and give you feedback.
Ask members of the target audience to play a prototype of your game and give you feedback.
Use your development log to record the feedback from this usability testing and any changes you have made to your game.
Save the final version of your game.