if you wanna load an image, you use the command Load Image
the load bitmap command is for something else. about the camera movement, you can use this code for maving with the w and s keys:
move camera KEYSTATE(17)-KEYSTATE(31)*5
this code moves the camera 5 points forward or backward. if the w key is pressed but the s key isn't, it does 1-0*5 and that's 5, so it moves 5 points forward. if the s key is pressed and the w key isn't, it does 0-1*5, which is -5, so it moves 5 points backward. and for the mouse rotation:
rotate camera camera angle x()+(mousemovey()/2),camera angle y()+(mousemovex()/2), 0
you can play a little bit with the values, and maybe use curvevalue. what it does, it rotates the camera on its x an y axis. on its x axis, it rotates the camera it original angle + the distance the mouse moved on the y axis divided by 2. it does the same for the x axis, but then with the distance the mouse moved on its x axis.