These are the steps that I'm using:

1. Open Deepin File Manager
2. Navigate to folder that contains ISO (it's a video DVD ISO)
3. Right-click on ISO, select "Open with" then select Disk Image Writer from list of apps.
4. Waits for Disk Image Writer to open
5. Once it's open, I cannot select the blank DVD as destination. It's grayed out.

But it's possible I'm doing it wrong too.

Thanks!