hello .. I am a beginner in the program and working on analyzing Sentinel data. How can I create a map like the one shown in the image? I hope to get a detailed answer
Your question is really difficult to answer because what you are asking is so open ended. The map you are showing has several different elements that you will need to understand how to work with:
Essentially you have to figure out how to work with layers in maps that are presented in a layout for outputting as either hardcopy (printed to paper) or soft copy like a .jpg or .pdf. All of these things have a whole host of properties to manipulate to display what you want. You will want to spend some time in the learning resources or help pages - you could start by searching for the various terms I've put in bold text. Welcome to the fabulous world of GIS.
It's nothing anyone can or is going to describe in a reply. You're also going to struggle if you only have ArcGIS Online. https://www.esri.com/training/new-and-retired-training/