1. Open the Secure Folder that contains the unlocked file.
2. Right-click on the file.
3. Select the Atakama menu.
4. Select "Lock".
5. Tap “Approve” on the Atakama Mobile app.
After performing the steps above the file will display a gray lock icon.
You can also watch this video guide:
(Right-click on the image and select open image in new tab.)