Karen, for seed starting, it may be better to get a seeds starting mix rather than potting soil. Seed starting mixes are a bit finer in grain and texture and they usually keep them indoors in the gardening center so they stay dryer. They are specially designed to be good for tiny delicate plants. The potting soil would be best used in a container that you would transplant your established seedlings into (a large pot on the patio) or, as others said, it can be good to work it into the garden bed since it will provide nutrients and organic matter.

Here is an example of a commercially available seed starting mix:
http://parkseed.com/seed-starting-mix...

If you are adventurous, you can try your own seed starting mix:
http://www.organicgardening.com/learn...