For manual mapping to work, all your HOTAS functions must be available in the "Game Controllers" control panel in Windows (I don't know the real name in English). I don't know if that is the case with your CH setup (is it USB or gameport?). Each controller may be represented separately if your gear is USB.
If you don't see any controllers in the Game Controllers control panel, then it means Windows XP doesn't see your controllers, and you won't be able to use them in AH. (I'm not sure gameport support is available in Windows XP; manufacturers have pretty much dropped gameport support in XP since the standard is now USB.)
First you have to go in Joy stick setup in order to assign controller functions to AH controls. Click on Select joystick.
In the Joystick window, select your Combatstick and click on the Select all inputs button. That sets all inputs to the available buttons and axes on the Combatstick. You'll have to manually assign functions for any other controller.
The principle is that you can arbitrarily assign a button number to any button on your gear. When you select the controller in the Joystick window, all its inputs will be listed in the Joystick inputs window, as they are named in the Game Controllers control panel. By selecting, for example, "X axis" on the right, "Roll" in the AH Control window and then clicking on the Set input button, you will assign the X axis of the currently selected controller to the "Roll" function in AH. You can do the same to assign the "Y axis" to "Pitch". Clicking the "Set all inputs" button will assign all the controller's available axes and buttons to corresponding AH controls.
For buttons, you assign available buttons on your controllers to arbitrary button numbers in the same way you assign axes to "Roll", "Pitch", "Rudder" or "Throttle". You could assign the trigger to "But 1" (button #1), but if you wanted you could assign it to "But 18". You have to assign each button on your controllers to an arbitrary button number in the AH Control window.
As I said, AH will do it for you if you select the joystick in the "Joystick" list then click on "Set All Inputs", but you need to do it manually for any other controller (i.e. for any USB Rudders and Throttle). When finished, click OK.
Then you're ready to map stick buttons to functions, like Gear Up/Down.
You do that in Stick Mapping. It works the same way as Key Mapping does, but you use the button numbers you assigned in "Joy Stick" setup. If you want your Pinkie switch to toggle gear, then in the Flight keys section you select Toggle Gear, you push on your pinkie button on your stick (which should highlight the corresponding "B##" button on top right of the window, e.g. "B5" if the pinkie was assigned to "But 5" in "Joy Stick" setup), then click on the Set Button button. You can repeat for each one of the 4 stick sets by clicking on the Set # buttons at the top of the columns. You do the same for all buttons you want to map. When finished, click OK.
That's all there is to it.