Please be sure to have downloaded and be running the latest version of the Trunk Desktop app which you can download here.
1. Inside of your project, select a previous commit from the commits panel.
2. Click the options menu next to the file name (3 small dots) and select Revert to this version.
3. You can now make any final changes you wish to make. Once you have done tweaking the design to finish reverting the changes, you will need to Finish changes, as you normally would. This will commit your changes to the master branch.
If you have any other questions, please give us a shout!