OK - this seems to be a question which crops up quite frequently but has no definitive, easy-to-find answer. So as an example I'll write a quick tutorial on how to reskin the Intercity Swallow Class 47. I'll make sure it's easy to follow for the less computer-savvy among us and I hope those with more of a technical background don't feel too patronised by my wording

This is actually very easy to carry out and simply requires a long-winded explanation, so don't be too daunted by the masses of text you'll see below!
First off, you'll need three things:
1) RSBinTool - download and install this to a location of your choice.
 | |  | RSBinTool v0.9 [64638 bytes] - RSBinTool.zip File ID: 17703 Date: 08 Nov 2007 - 4834 Downloads |
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2) A graphics package such as Photoshop or Paintshop Pro. Alternatively there are some very good free packages such as
The GIMP or
Paint.NET
3) Patience. If you have not reskinned before you will need to learn to use the various features your graphics package has on offer. For this there are plenty of tutorials available on the net if you search about. If you have, then there are still .bin files to get to grips with. Once you know how it's easy though.
Now for the gritty stuff
- To start with, you'll need to make a copy of the folder containing the locomotive, carriage, wagon or object you want to reskin. These can all be found under Rail Simulator\Assets\Kuju\RailSimulator - Railway vehicles are contained within the aptly-named "RailVehicles" folder, which is itself subcategorised into Diesel, Electric, Steam etc... In this case I need to go into "Diesel\Class47 and select the folder "ICS".
Make a copy of the folder and rename it to whatever you want, in this case I'll name it IC_Exec, since I'm reskinning the loco into Intercity Executive livery.
Now, before you start to reskin you will need to alter the name of the locomotive. To do this you need to find the .bin file located within the "Engine" subfolder, which in this case is called "class47_ICS.bin". No need to rename it, simply copy it and then paste it into your main Rail Simulator directory.
Now, in your Rail Simulator directory, locate the file
serz.exe and drag the .bin file onto it.
This will convert the .bin file to a .xml which we will then be able to edit using RSBinTool. A black DOS box will pop up for a second, after which you should see a new file in the folder called - in this case - class47_ICS.xml. If you want you can now delete class47_ICS.bin. If you need it again you'll still have a copy in the IC_Exec folder you just created.
Now you are ready to launch RSBinTool. If it's the first time you've used it, you'll need to tell it where your main Rail Simulator directory is. Once you've done that you're ready to start. Go to File>Open>XML File and select your newly-created .xml file.
To many, this will look like a pile of gobbledegook. It is, essentially. But thankfully the bits we need to change are in plain English. The first part is the "Name" section. This can be whatever you like, but should not be changed once you have started distributing the asset or using it in scenarios, as changing it is likely to cause "scenario failed to load" errors since the sim will no longer be able to find the asset. The second part is the "DisplayName" section. Again this can be whatever you like, but in contrast to the "name" section can be changed by the user to suit their tastes. For example I have renamed all my Class 47s to be listed as "Class 47 - Operator - Livery". Choose carefully as this is the name that will be displayed within the sim, for example in the editor's rolling stock list. Once you're done, go to File>Save and select "yes" when asked to overwrite.
You will now need to go back to your main Rail Simulator folder and drag the
.xml file (not the .bin file) onto serz.exe. This will reverse the process and convert the .xml to a .bin file. If you didn't delete the original .bin file, it will simply be overwritten. Once that's done, copy or drag the new .bin file to your IC_Exec\Engine folder, and overwrite the old one. Your locomotive now has a new name. If you want to check it in the editor, simply delete the blueprints.pak file from Rail Simulator\Assets\Kuju\RailSimulator and launch the sim
