Polymorphic associations

my profile model has_many :pictures, as: :imageable and so do several
other models
my picture model belongs_to :imageable, polymorphic: true
in the pictures table fields imageable_id and imageable_type have both
been
migrated
ok now i create a new_user_profile_picture how are the values for
imageable_id and imageable_type gonna be inserted into the pictures
table
please? ~ thanks