Adjusting front suspention on Suntour 63 mm

I have a Gepida bike with a Suntour Nex E 25 63 MM front suspension fork. Does anybody know how to adjust these? They feel like they're either locked or set on the stiffest level. I would like to make them softer. I removed the top cap and there is an arrow that indicates it can be turned, but no markings to ensure both forks are set the same. There are plastic teeth that may require a special tool, and it looks like a hex key fitting in the center. Thanks for any tips, links, advice.
 
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