Explain the shared goal, identify your contribution, and keep the overall result separate from what you personally did. Working as part of a team is valuable experience. You do not need to claim sole responsibility to make your role meaningful.
For example, you might have gathered information, kept a schedule current, or helped colleagues prepare. Describe those actions specifically and acknowledge that the result depended on others too. If you are unsure how much your contribution changed the outcome, say what is known rather than assigning yourself an unsupported share of the credit.