So? The reason why you want to change doesn't alter the method that you change it.
How depends upon your computer. What is your non-Intel GPU? If it's Nvidia then it's possible to have a right click menu option called "Run with graphics processor ->" or you start the Nvidia Control Panel and navigate to 3D Settings -> Manage 3D Settings -> Program Settings and you can configure minecraft.exe, java.exe and javaw.exe to all run on your high perfromance GPU. If you have an ATI GPU then the method is different.
Your driver may automatically switch, or you may be able to give it a list of programs with their corresponding GPU assignments.
http://www.minecraftforum.net/forums/support/modded-client-support/2315636-minecraft-crashes-if-i-select-a-shaders-mod#c7
How depends upon your computer. What is your non-Intel GPU? If it's Nvidia then it's possible to have a right click menu option called "Run with graphics processor ->" or you start the Nvidia Control Panel and navigate to 3D Settings -> Manage 3D Settings -> Program Settings and you can configure minecraft.exe, java.exe and javaw.exe to all run on your high perfromance GPU. If you have an ATI GPU then the method is different.