You can purchase all items in Marketplace. If you hoover your cursor over it, you will see a drop-box of items from which you can choose Templates, Themes or Licenses.
Procedure for purchasing templates, themes or licenses is the same.
Let's say you are searching for a template. In Marketplace drop box choose template.
You will see the a grid of all templates from which you can browse and choose. Or If you have a specific template in mind you can search products and find what you need.
If you found the right template for you click on it and you will see description and template details. If you are sure that's what you want click add to cart.
Once you selected what item you need click on view cart
You can add multiple items to you cart and you can always return and add more.
If that all you need click on Proceed To Checkout
Last step is to fill in your Billing Information and Place Order