Where should I start??

[Rosalind]

For the soil, you can get a test kit at any garden center that will tell you pH and nitrogen, phosphorus and potassium levels. pH for most things should be 6-8. If the pH is lower than 6, you can sprinkle agricultural lime, higher than 8 sprinkle rock sulphur. For low nitrogen, add fishmeal or composted poop, for low potassium add greensand, for low phosphorus add bone meal or rock phosphate.

It looks a little silty to me. The compost & manure recommended by Pat & hermeneutics will help.

 

[Blue Ridge Hillbilly]

With a 10 X 20 foot garden to work with, I would like to recommend a book such as "Square Foot Gardening". I think this book has been revised in recent years. What you need to know is how to garden "intensively" in a small area. This book will tell you how to get the most out of a very small space. In the mean time, you can do some soil testing to see what your plot needs if anything. Happy gardening.