First thing first. You must have an account with ShapeBootstrap. After successfully creating the account, login to the marketplace.
Go to your ShapeBootstrap account dashboard. You will get the Start Selling Yours link.
Clicking that button will bring the Start Selling landing page.
There you will get the Upload Now button.
Hit the Upload Now button. It will bring the item uploader page. Provide necessary information and finally upload your item.
Don’t forget to read the submission guidelines to ensure that you are aware of the standard practices on the marketplace