A revision entry can be expanded to list all the files affected by the revision - just click the entry field:
Click it again to hide the files.
Each listed file entry can be in turn expanded to show its unified diff - just click the file name:
To open a revision, click on its message text or ID. You’ll be redirected to a revision view where all the files included in the revision will be displayed along with a unified diff underneath each of them:
If this revision is covered by a review, you can go to that review or detach the revision from it:
Or, if it’s not part of any review, you can create a new review for it or attach it to an already existing one:
You can always see where you are in the project and go back to a revision view or a project home view using the navigation bar at the top: