This guide will help you find a current list of boards that will work with DK IoT Studio. The board list changes as more hardware is made compatible with the Studio.
Then once you are logged in you should be in the dashboard. Located on the left side there should be a navigation bar. Select the projects icon.
Once there select new project.
This will bring up all the current boards that work with DK IoT Studio.
To purchase or get more information on the board you can either plug the part number into the Digi-key search engine, or click on the shopping cart icon to the right of the manufacturer. From the cart you can click on the blue highlighted part number.
This will take you to the main page of the part where you can view the product attributes, view the datasheet and many other options.