This detail is taken from the back of the picture. The small bud at lower left is at about the extent of the depth of field and is still in focus. The three small dots at the bottom are the upper part of the main flower. But the flower in the background is definitely beyond the depth of field and is therefore out of focus. The lens was not much more than an inch from the main focused flower.
Depth of field is simply another tool a photographer has when composing a picture.
You should think of it as separate from focus but it also helps you with the basic focus setting. As you study the preview in your viewfinder, study carefully the focus of all the elements that are at different distances. Try adjusting the point of focus a bit for you are actually adjusting the depth of field. Study the results of the depth of field and if you don't like where it is, adjust the point of focus which changes the range. These are all controls and adjustments that you should learn and commit to subconscious memory and recall as you work.