You will put in enough materials to create snow man via the Create-A-Tron.

Round 1:
Nose: Carrot
Hat: Hat
Eyes: Button (Clothes)
Arm: Branch
Scarf: Scarf
Snow: Snow (Pile)

Round 2:
Nose: Parsnip
Hat: Top Hat
Eyes: Rock
Arm: Stick
Scarf: Kerchief
Snow: Snowball

Round 3:
Nose: Vegetable
Hat: Snowhat
Eyes: Coins
Arm: Twig
Scarf: Headscarf
Snow: Snowflake

Other Answers:
Nose: Carrot Nose, Clown nose, Salsify

Scribblenauts Remix 7-4 Cheats Hints gallery:
7-4-1-a: Use the Create-A-Tron to make a snowman.
7-4-1-b: What does a snowman wear?
7-4-1-c: Use a button and a vegetable for the snowman’s face.