Planting flower seeds in containers outdoors in NM?

I have Snapdragon, Petunia, Cornflower and Gazania seeds, which I was thinking of planting in containers outside of our house in NM. We bought good soil. Do I need to put mulch on top too (around where the seeds are), or just keep them adequately watered? Obviously, I'm new to gardening, any suggestions will be appreciated. Thank you