First, check to see that the species you received are native to your area. Many pre-packaged "wildflower" mixes are not native to North America, let alone your particular region. Some in fact, are invasive or weedy. A good website to find natives in your area is PLANTS, a USDA database. The URL is http://plants.usda.gov/ Another good one is the Native Plant Database http://www.wildflower.org/plants/

Next, a good site to find seed germination data and cultural guide is Prairie Moon Nursery in Minnesota. http://www.prairiemoon.com/
They have an especially good section on how to seed new prairie plantings. Prairie Nursery in Wisconsin is another good one.

And don't forget native grasses, most native prairie forbs (wildflowers) are the minority in prairies, and require the sturdy grasses for protection and to keep them upright. Most are very beautiful in their own right and provide food and shelter for birds.

A little bit of research on your part now will help avoid a lot of headaches and disappointments in your garden in the future.