If you can't seem to edit your files, please make sure that:

• You're logged into your account.
• You're an editor in the same workspace as the file.
• You haven't reached this month's limit. On the Free plan you can create up to 50 board objects and 50 doc blocks per month. Once you reach either one, you won't be able to add new objects or blocks until your allowance resets at the start of the next month, or until you upgrade.

The number of boards and docs you can create isn't limited on any plan, including Free. What counts towards the Free allowance is the objects you add to a board and the blocks you add to a doc.