As you are a beginner you need time to grasp a few things, but don't worry sir! I'll tell you the process and the rest you will do by practice.
Here is the Complete Process:
The above images you posted are all digital painting designs
First everything starts with the sketch.
I recommend you buying a tablet or sketch papers if you want to start now, The cheap tablet I can recommend is Huion 12', one which will help your process even faster.
You must have some painting or designing skills (However again practice makes the man perfect).
Start sketching your ideas and don't worry if it's rough.
Here is the important part: Which software? (Well, I highly recommend using the Adobe Illustrator or Photoshop which are my personal favourite) Let's start with Illustrator then.
After sketching your ideas you need to make separate layers for each design you are making (for example: sketch, line art, colors, shadows and effects).
First, make a sketch.
Second, make line art using the Pen Tool or Brush Tool (Make sure it's clean).
Third, add colors from the Live Paint Bucket Tool.
Fourth, add effects and shadows.
The last, which is the most important, is making all images super attractive. Use Photoshop to edit it as a photo. Just add some effects. You can also use some plugins for auto effects and more.
Well, there are lots of videos for you to get started, like making line art and sketching but here I can only give you an idea.
Hope that helps. Please let me know and ask anything you like.