Just plant it in the ground in ordinary garden soil, preferably not heavy and waterlogged, in a sunny position.

They're supposed to like a well-drained soil in a sunny position but in my experience they self seed everywhere in clay/chalk, sun/shade, even between paving in shingle with membrane underneath.
The babies are easy to pull up though if you catch them young enough. Of course, this wouldn't happen if I chopped off the dead flowers before they seeded!