The End is the Beginning
When a prairie plant comes to the end of it’s life it produces seeds. Seeds can be dispersed in a variety of ways. However, if you want to start a prairie, you will want to collect them before nature takes them away.
One solid way to start a prairie is to borrow from an established one. Not every prairie is the same, so it is better to know more about the site you are creating along with the site from which you are borrowing. Conditions, such as soil, sunlight, and hydrology will impact the variety and success of plant development, so it is best to see what plants grow well in an area similar to the area you are developing.
Once you have found the site(s) that you plan to model your prairie after, you can start collecting seeds. Of course, plants go through their life cycles throughout the growing season. In order to collect seeds at the proper time, you must know when and where to collect them.
Then, your job is to collect, collect, collect.
Unless of course you have enough discretionary income to purchase them.