This might seem like a simple thing, but I can't find the options that Jira's help lists.
I'm trying to make some child issues assigned to me as done, but I don't see how.
So, I've got a task like this:

I've completed the editing and CMS upload and want to make those complete. But when I click through on the task, what I see is:

I have no idea what feature to use to mark things as complete. When I click that blue "Editing" button there is a "Complete" option but that doesn't actually mark things off on the child issues list.
Only thing I can think of is that the "Reporter" is another team member, so maybe they have the option to mark as done, and I don't?
Feels like I'm missing something obvious, so please let me know what it is.
Thank you very much for any help!