Navigate to the board view that you want to edit the default title for by clicking the boards icon, and selecting the appropriate board as shown below for leads.
Click the 'Show menu' button as highlighted below.
Select 'Settings' from the list shown.
Locate the title 'Document header' (at the top of the page) and edit your default title in the text box shown below.
Once edited, click the tick in the bottom right corner of the page to save your changes.
The default title for all documents in this board has now been changed.
If you wish to change the title of one document specifically without changing the default title for all documents, please consult our article: How to Edit the Title of a Document.