Navigate to the Projects tab and click the Custom Fields tab near the top of the screen.
This will open up the Project Custom Fields tab where you will see existing Custom Fields (if any). To create a new Custom Field, click the blue New Custom Field button in the upper right hand corner.
After clicking Create Custom Field, the menu will change and you'll be able to add in your field details.
Enter the name of your custom field and pick from available field types. The field types are Text Field, Dropdown Single-Select, Dropdown Multi-Select, Pill Single-Select, Pill Multi-Select, Badge Single-Select, Badge Multi-Select, URL Link, Firm Member Single-Select, Firm Member Multi-Select and Date Picker. If you select one of the dropdown options, you will then be prompted to add the field options you'd like in the dropdown menu as seen in the screenshot below.
If your field is a Text Field, you'll be able to mark the field as sensitive, which will mask the information on the project profile with the option to reveal it. The sensitive option is not available for the dropdown field types.
After you've entered all the required information, you can click Create to create the field. This custom field is now available to be edited on any individual project or series profile!