Starting with KSP 0.14, the game supports custom part behaviors called Plugins. Defining custom behaviors allows you to create totally new kinds of parts, such as flight control computers, new types of fuel supply chains, etc. You can then add these to the game in the form of plugins. These DLLs can be loaded on any platform that can run KSP.
READ THE POSTING GUIDELINES BEFORE PUBLISHING YOUR PLUGIN
To use a Part Module Plugin, just drop the DLL into KSP/Plugins. If the folder doesn't exist, you can create it.
To start with, you need to decide which IDE you will use. An IDE is a program that helps you to write code (in our case the language C#). Listed here are some of the most popular options. Green means it is available for that OS, and red means it isn’t available.
|Visual Studio||Commercial||✓ Yes||× No||× No|
|MonoDevelop (aka Xamarin Studio)||LGPLv2 / MIT (Free)||✓ Yes||✓ Yes||✓ Yes|
|SharpDevelop||Open-source (Free)||✓ Yes||× No||× No|
Now, you can get started.