I think all of this actually is in the manual:
how to set the center
5.8.1.2 Profile Settings
"Hotkeys
Hotkeys allow you to map keys or buttons on other input devices to perform functions in the TrackIR software. You can select the keys to be used, turn the hotkey on or off, enable toggle mode, and trap the hotkey. Select the hotkey you wish to edit (Pause, Center, or Precision) from the dropdown menu."
"Center
The Center hotkey allows you to re-center your in-game view. Every time the Center hotkey is pressed, it re-defines your current head position as the new center."
how to set up how far i am from the windshield
3.5 Hardware Placement
"Position the device further away if you�d like more room to move around. (We recommend between 2 and 5 feet.)"
what the blue, red and green arrow means
There aren't any arrows in the TrackIR 5 software that I'm aware of.
what the green spot means
If you mean the dots on the camera view:
5.9.2 Camera View (2D Tracking Data)
"Undesired light sources in the camera�s view will also be exposed in this window. Green objects are being tracked by the camera while red objects are not."
If you're referring to the green LED lights on the camera:
4.3 Camera Status LED indicators
"- Left Green : A clip IS being tracked.
- Right Green : A TrackIR Enhanced Title IS running and has registered with the TrackIR software to receive tracking data.
- Both Green : A clip IS being tracked, and a TrackIR Enhanced Title IS running and has registered with the TrackIR software to receive tracking data."
why it dissapears some times
That depends on which dot you're referring to, but in all likelihood, it's because the camera has lost tracking and can't see all of the TrackClip.
what the Camera view does
5.9.2 Camera View (2D Tracking Data)
"The Camera View is a larger version of the Camera Window. It shows what the TrackIR camera is tracking, and what is in its field of view. This helps you adjust the position of yourself and the TrackIR camera to get the best range of motion and tracking results.
Undesired light sources in the camera�s view will also be exposed in this window. Green objects are being tracked by the camera while red objects are not. Other important tracking data (frame rate, tracking mode, and number of tracked objects) is located at the top right corner of the window."