Checkout fields editing

Hi I’m using these steps to create checkout page:
Quick steps to create checkout layout:
Step 1. Go to Dashboard -> Layouts -> Checkout and click on the “Add new” button.

Step 2. Set layout type to “Checkout form” and write your layout name.

Step 3. Click on the “Create layout” button.

Step 4. Fill your custom layout with sections and special elements.

Now my question is how can I edit fields in form? I want to edit mandatory fields.