So let’s get on with the whole procedure in short:
The first step is entering your desired theme name in the first input box.
Make sure theme name should not be empty.
Enter the author name in the next input box and author’s Email on its next.
Enter the theme URL on the fourth box. The URL as the most of you know would be in the form http:// or https://
In the next step upload an image of the theme. You can either drop or upload the image here. (Note: You’re only supposed to upload images with a JPG extension)
You can add some description about the theme below the upload space.
Then on Add Menu section, you can add the number of menus you wanted in your site by a single click.
Click on the "+" to add new menu.
You can click on the "-" to remove a menu then it will disappears. If in case you’ve accidentally removed all things from add menu section, reload the page. This will bring back the whole page to normal.
On the Add Sidebars section, add all that you want to display on the sidebars and then you’re finally good to go.
Click on Generate Button then Wordpress Theme zip file will be downloaded automatically. After Download Complete you can upload into Wordpress and you can use it. If any issues you face with this theme you can send to firstname.lastname@example.org