does any one know to make a plane on fsx

If you mean a plane skin then there are two parts, first editing the DDS texture files and second editing the plane cfg file to add the menu entry for it.

Easiest to use an example. Grab the Tiger Moth here: http://www.antsairplanes.com/downloads/AntsTigerMothV110.zip

It is an installer but for now just install it to something handy like My Documents, not the program directory.

Go to the install folder -> SimObjects\Airplanes\Ants Tiger Moth. Copy and past the Texture folder and rename the copied folder to texture.Xsimulator

For fun I modified the Xsimulator.net logo so it was transparent, then used Paint.net to open the wing DDS files, added a layer, manipulated the logo so it would render the right way, which can be a bit confusing, then saved it as a DDS, saying yes to flatten the image. The results are attached in the zip file, so if you want you can use them as a template to figure out which way the images are oriented.

You could use Gimp, there is a DDS plugin for it, but you have to get the DDS settings right. Paint.net is correct for DDS skins by default.

Once you have the skin customised you then need to modify the aircraft.cfg file which is in the Ants Tiger Moth directory. Use Notepad open the cfg file and you will see entries 1-7 describing the existing skins. You need to add another one, the two main things you want to change is the Title, so it is easy to find, and most importantly texture=Xsimulator, which identifies the new folder we made earlier 'texture.Xsimulator'. I also altered the Description in the following example. Just copy and past below after the existing [fltsim.7] entry in the cfg file and save it.

[fltsim.8]
title=Tiger Moth Xsimulator
sim=Ants Tiger Moth 00
model=round
panel=
sound=
texture=Xsimulator
kb_checklists=Ants Tiger Moth 00_check
kb_reference=Ants Tiger Moth 00_ref
atc_id=BMPY
atc_id_color=
ui_manufacturer="De Havilland"
ui_type="DH82 Tiger Moth"
ui_variation="Yellow G-BMPY"
ui_typerole="Single Engine Prop"
ui_createdby="Ant's Airplanes"
description=The De Havilland Tiger Moth is one of the most famous aircraft ever built. This is a custom Xsimulator.net skin for the Tiger Moth.

Now copy the Ants Tiger Moth folder and paste it into your FSX install directory inside -> SimObjects\Airplanes\

Now when you go to FSX you should see the Xsimulator skin entry, your own description and the preview of the modded skin.

No you don't need to change those.

The entries name and describe the model, the only ones you need to change is the title, so it is easy to find in the menu, and your new skin name: texture=Xsimulator

FSX will know where to get the texture you made as long at the is the same naming convention as you used to renamed the texture folder in the first place. Remember the early step where I said to copy and past the Texture folder and rename the copied folder to texture.Xsimulator. The second part of the name after the dot, texture.Xsimulator, is what you use for texture=Xsimulator

Yes if you have different texture folders for an aircraft then each one has the next number in the cfg file for the menu entry.

I expect so.