Therefore API > API Reference > Classes > TheFieldList > Methods
Add
Adds a field number to the list.
Name
Description
Add (TheCategoryField)
Adds the field number of the specified TheCategoryField to the list.
Add (int)
Adds the specified field number to the list.
Add (string)
Looks up the field number for the specified field ID and adds it to the list.
Please check the help pages of the various overloads for the exact syntax in Visual Basic and C#.