Hi @lisapaloma, welcome to the forum! It looks like you mainly use the Android phone app for your observations, correct? To edit the geoprivacy of an individual observation in the Android app, I will have to let someone more familiar with the app chime in, since I mainly use the web site.
If you can use the web site (inaturalist.org), you can find instructions and screenshots for changing geoprivacy on batches of observations by clicking here:
https://forum.inaturalist.org/t/change-geoprivacy-on-multiple-observations-at-once/23570
To change a single observation on the web site, go to the observation detail page, and click the blue edit button at upper right (not the down arrow next to it). At bottom center, right below the map, is a box to Change geoprivacy. Be sure to click Save Observation after making the change.
And yes, as already noted, the default geoprivacy for iNaturalist is always “open” (unless it is a threatened species), and users can’t set a different default in their account settings. Obscured or private geoprivacy always has to be specified for each observation or batch of observations that you upload.
Hope that helps.