Step by step process,
First create a folder ( name your folder ) and add the image/images that you want to upload in Readme.md file. ( you can also add the image/images in any existing folder of your project. )
Now,Click on edit icon of Readme.md file,then
![](relative url where images is located/refrence_image.png) // refrence_image is the name of image in my case.
After adding image, you can see preview of changes in the, "Preview Changes" tab.you will find your image here.
for example like this,
In my case,
![](app/src/main/res/drawable/refrence_image.png)
app folder -> src folder -> main folder -> res folder -> drawable folder -> and inside drawable folder refrence_image.png file is located.
For adding multiple images, you can do it like this,
![](app/src/main/res/drawable/refrence_image1.png)
![](app/src/main/res/drawable/refrence_image2.png)
![](app/src/main/res/drawable/refrence_image3.png)
Note 1 - Make sure your image file name does not contain any spaces. If it contain spaces then you need to add %20 for each space between the file name. It's better to remove the spaces.
Note 2 - you can even resize the image using HTML tags, or there are other ways. you can google it for more.
if you need it.
After this, write your commit changes message, and then commit your Changes.
There are many other hacks of doing it like, create a issue and etc and etc. By far this is the best method that I have came across.