Welcome aboard. Enjoy the ride.
We look forward to seeing more posts and samples of your work.
What is the brand and model number of the flash. Please complete your profile and provide more details on how you are using the flash so we can help you.
That is not a TTL flash; according to the product description "Flash does not provide TTL functionality. Exposure must be controlled manually by adjusting your camera's aperture, shutter speed or ISO values."
If you want something that works in Auto mode; you are better off spending a little extra on something like this:
You need the user manual for the flash, it is quite different than anything today.
But there are online instructions here https://www.youtube.com/watch?v=Jvcax6E-CCE That should get you going.
It has some very old style automation, but it's nothing like automatic modern TTL flashes.