How to compile and use an external class

[Some Guy]

I am busy learning D and I want to be able to use classes now. I am
used to programming in C# where it does everything for you and you
don't have to think about this kind of thing so I now have no idea
how to compile a program from the command line that uses a class in
another source file.

I have a source file called MyProgram.d which contains the main
program and I have a file called MyClass.d that contains a class
called MyClass. I want to be able to create an instance of MyClass in
the main program but I don't know what to type to compile it the
command line. This is what I have tried so far which doesn't work:

dmd MyProgram.d MyClass.d

Thanks in advance for your help.