To set up a matter so only you can view it, you'll need to enable a feature called File Security.
To do this, follow the steps below:
Log in to One Office and open the matter that you'd like to lock.
Click the Matter button (it has a little brown briefcase next to it).
At the bottom of this screen, under the field which says App Code, tick File Security.
Note: If this box is greyed out, check all the fields are filled out correctly.Click the green man silhouette button next to the tickbox.
From the list of fee earners, next to the user who requires access, tick the box in the Has Rights column. Note: Make sure you include yourself if required.
Click Ok.