Once the challenge has started, you can start making submissions. Follow the steps to make your first submission:
Goto to the challenge page.
Click on "My Submission" and you will be redirected to the submission page.
On this page, click on "+ New Submission" and follow the on-screen steps.
After successful submission, you will be able to see your score (if the challenge has enabled auto-grading).
Some important points regarding your submission:
Make sure you read the submission guidelines of the challenge carefully.
The submissions are usually auto-graded. If the submissions are not auto-graded, it may take up to a day to see your score.
You must abide by the rules of the challenge.
You can make up to 20 submissions every day.