Option 1
1.1 click hub ( because this is arcgis online, it is called hub, if you are in portal, it is called sites)
1.2 click manage
Option 2
arcgis online are different from arcgis portal, arcgis online have Open data tab let you configure, while arcgis portal don't have this open data tab
arcgis portal don't have this open data tab
Make sure, you click Anyone, otherwise, you will not see any site, because Mine option means only show your hub site, while you may not have any
Why apps sites don't show my open data hub site
it is because your hub site type is not hub site, instead your hub site type is just web mapping application, this is not usually happen. But it does happen sometimes like my case. What you can do is just search key words open data, against all content, you should be able to find it.
Here is why open data site isn't hub site type, instead it is web mapping application, see the created year is 2017. back to that time, hub site type isn't appear yet.
How to make change updating this open data hub site, you click configure
