JustShop theme has custom post types for Cakes/Portfolio.
FYI: You can find instructions about setting up portfolio here in documentation too.
First → Create Portfolio/Cakes Items. You can go to Cakes/Portfolio → Add New and fill in your entries for each item. See the screenshot below
Second → Setup a page to display those Portfolio/Cakes Items. Create a new page and name it as you like. Then from 'Page Attributes' section, choose 'Page Template'. See the screenshot below
You will find 3 Page templates related to portfolio:
- Portfolio One col
- Portfolio Two col
- Portfolio Three col
As their names explain, the only difference between these page templates is the number of columns for the portfolio items page.