To start, press the Sample Merge button (in left-side Files panel) or upload your own DITA files by drag and drop or pressing the Upload button (button panel - lower left) and entering the file URLs. Sort the file buttons now shown in the Files panel using the toolbar arrow buttons, ensuring the 'common ancestor' (suffixed '-base' in the sample) is placed first.
Press Merge, after around 30 seconds (a timer is displayed) the server should respond and the merge result will be shown in place of this text. You're now ready to review changes by switching from the Files panel tab to the Content or Attributes tabs. The Accept and Reject buttons switch your review modes, they're either 'one-off' or 'sticky' if you press them twice.
There's much more of course, so please press the XMLFlow button (toolbar - top left) for more help.
Thanks for trying out XMLFlow, it's free, but this app is partly a study so any feedback would be greatfully appreciated and will help improve the product.
Please visit the application website for further information.