The Settings pop-up automatically opens up once a new project is created.
For an already existing project, the settings can be accessed at project level by project creator and account owner. Clicking the 
icon will show the settings option [highlighted by the red rectangle in the screenshot below].
The 'Punch settings' pop-up screen is shown below,
Add Custom Attributes Section:
The punch list settings pop-up section lets you enter the custom fields. The application will provide the maximum 5 custom fields. To add more custom fields after entering the first one, you need to click on the 
button. Clicking this button will make a new textbox field appear below the existing one where you can enter the next custom attribute. This is shown in the screenshot below,
After saving the custom attribute these fields will appear on the Create punch list screen at document level and project level. The custom fields cannot be deleted once created and saved.
For example, enter a custom attribute called 'Number'. This attribute will appear as a field on the Create punch list screen as shown in the screenshot below,
Entering data on a custom attribute field on the Create punch list screen is optional.
User can enter alphanumeric values/texts on the custom attribute fields on Punch creation screen.