Objective-C method description (doc comments)

I'm currently learning Objective-C and need to know how to write a method description. I'm having a lot of difficulty learning how to do this in Objective-C.

In Jave we have this

/**
< h2 >MethodName</ h2 >
< p >Various Description, can use html with images etc.</ p >
*/
private void methodName(args[]..)
{

} 

In objective-c where do I place the description? Also does this to be in the header file or the implementation file?

//Within Implementation?
- (float)gteHeightPercentage:(float)percentageToGet
{
    return self.view.bounds.size.height * percentageToGet;
}

//Within Header?
- (float)getWidthPercentage:(float)percentageToGet;