# Basic syntax:
pandas_dataframe['new_column_name'] = ['list', 'of', 'column', 'values']

# Note, the list of column values must have length equal to the number
#     of rows in the pandas dataframe you are adding it to.

# Add column in which all rows will be value:
pandas_dataframe['new_column_name'] = value
# Where value can be a string, an int, a float, and etc