Click on the Controller icon next to the settings, info, and star icons on the right top side, below the Revolver 360 ReActor Image.

This brings up the Controller settings. Click on 'View Layout'

Click on 'Left Joystick' option. In the screenshot I have already configured it,
that's why it shows up as 'Standard Dpad' but your setting won't be this yet.

Change the 'Left Joystick Behaviour' to 'Directional Pad'. Then change each
of the joystick positions to each of the Dpad directions.

Once you've done this, click the back button, and select apply settings.

You should have your own custom controller settings for this game now.
Which you will see under 'Your Layouts'

Please note - I did notice that after shutting down my computer, going to bed, then waking up the next day and playing the game, these custom controller settings had been lost and reverted back to the old ones. So you may need to repeat the above process. Once I repeated the setup, I restarted my computer and went back to the game, the customer controller settings did not disappear and were still there. So I don't know, maybe I did something the second time that I didn't do the first time. I also noticed that now all the left stick settings where appearing under the 'Directional Pad' List, as in the screenshot below. That wasn't showing up when I originally did the first custom setup. So maybe make sure that the 'Directional Pad' stick list is there to confirm you've done it correctly.