First, you'll need to open Preferences, and then insert the OpenGrok URL.
Go to menu, open Tools => Preferences.
2. Edit OpenGrok URL settings to have below value (if using open source, or any other custom URL if using your own)
Finalize the setting with Save Settings button, and then you may try the new feature by right-clicking some element in the view and select Jump to Source which will open your browser tab to show the element in OpenGrok.
For example, here we show the code from coord.h in inkscape project:
My project is more complex than that, what to do?
In case your project is more complex, e.g. the repository is named differently in Softagram and in OpenGrok, then you may need set also OpenGrok Strip Path Level to have custom value (default is 2). For example, in case your repo is named foo in Softagram but bar in OpenGrok, you need to use this method to get it working.
OpenGrok URL: http://code.metager.de/source/xref/bar
OpenGrok Strip Path Level: 3