There are two ways to create a new design: Create it from scratch (starting with a blank schematic), or start with an existing design by first copying it as your own.
Note that the terms "design" and "schematic" are interchangeable.
Create a new design from scratch
In the top banner, hover over Designs and select the Create Design option.
A blank schematic will appear and you can start adding parts and wires
The design will have a default title which you can change in the right sidebar
The right sidebar has other useful information such as the design description, tags (for searching) and the group where the design is saved.
Copy an Existing Design
Find the design you want to copy by browsing or searching existing designs.
Click on the design to open it where you can make changes
Before or after making changes to the design, click on the Save As icon in the schematic toolbar
You will see a small dialog where you can specify the design name and the group where the design is to be saved.
You also have the choice to copy over the design description and the tags