My dear Sis Hurster
Yes, indeed, mid-September is way way too late to plant the vegetables you mention. But all may not be lost. There are some cool-weather greens that you may consider planting even now. Spinach, arugula (no political jokes now,) kale, swiss chard, even lettuce, and a host of Asian (what used to be called Oriental) greens can withstand low temperatures, with protection, down to 20 degrees!
As for the general hints you ask about, here are some ground rules: You want your soil to be well worked, rich in organic matter such as compost (the more worms the better.) Find a sunny spot in your garden, you can even interplant your veggie greens with your flowers, but you will need sun. You can sow seeds right into the ground, in rows or in whatever pattern you wish. Follow the instructions on the seed packet for thinning and care.
There you are, voila! In a few weeks, you will have veggies for salads and soups.
Next spring, you can plant your carrots, melons, zucchinis, tomatoes, etc. These may prove a wee bit more complicated, but nothing you cannot tackle, Sis. So write me again in the late winter or early spring, and we can chew the cud over planting the fruiting vegetables.