To reach this page, first click on the "Contacts" tab at the top of your account:
Next, click the "Manage Fields" button:
This will take you to the "Manage Contact Fields" page where you can create, update, and delete your contact fields. You can also see which contact fields are "featured", and where they are being used within your account.
Note that you can also see each of the three types of contact fields you've created:
This allows you to easily view and edit your contact fields based on whether they are text, date & time, or numeric.
Create a New Field
You can create new contact fields via the "Manage Contact Fields" page or within a flow using the Update the Contact action.
First, click the "Create Field" button on the "Manage Contact Fields" page:
Then, give your field a name, select the field type, and choose whether you'd like it to be "featured" on your contact's page or not:
Within a Flow
To create a new contact field in a flow, you must add an 'Update the Contact' action:
Then create the new field name and the the variable using @results.[variable_name].
Click "Ok" and you'll see that the new contact field will be updated in the flow:
You can then go into your "Manage Contact Fields" page to view that new contact field, its corresponding variable, field type, and where it's being used:
Learn more about adding and updating contact fields here.