Here's what Google has to say about the contest:
"For this year’s contest, students can create a doodle that tells the world “What makes me…me.” Kids have all kinds of things that make them unique, so they can use all kinds of materials to create their doodles, from crayons, to clay, to graphic design, even food and video games.
Students in grades K-12 are invited to take part in the 2015 Doodle 4 Google contest. Like all Google Doodles, each doodle must incorporate the letters G-o-o-g-l-e. One national winner will also receive a $30,000 college scholarship."
The online entry form is HERE.
Here is the winning doodle from last year.