When you get around to sowing them, you have a choice about whether you sow the seeds in open soil, or in trays and pot them on.
If you sow in open soil there is risk of being eaten by birds and slugs, and germination and growth is subject to the weather.
If you sow in trays, then this is not as simple as sowing other seeds, because the different species of wildflowers will germinate at different times. So it needs a large tray, with seed spread sparsely. Alternatively, seeds can be sown individually in modules, and then potted up individually (which is the best way).