Joining the Scratch community
If you're planning to work with the online project editor on the Scratch website, I highly recommend you set up an account on scratch.mit.edu so that you can save your projects. If you're going to be working with the offline editor, then there is no need to create an account on the Scratch website to save your work; however, you will be required to create an account to share a project or participate in the community forums.
Let's take a moment to set up an account and point out some features of the main account. That way, you can decide if creating an online account is right for you or your children at this time.