Go to youtube.com, click on your profile (your little picture on the right), go down to your settings, click channel status and features, under the channel category you can see that you need to verify your phone number to unlock special features like long videos and custom thumbnails.
Ask your parents if you can use their phone number and then select your country, enter your phone number or your parents. It will send you a text message verification code. Enter that code in the text box.
Your channel is now verified!
Go to Canva.com, create a FREE account, click the create design button.
Here's a video on how to create a canva account. Select personal account.