How do I mark an order as complete?

I did send a message to Vinted support, but their chatnot didn't help and they may not respond to me for 48 hours. I feel like I'm supposed to see a button in the item thread that let's me mark the order as complete. How do I do this?

This is my first Vinted purchase. Also annoyingly, I got the order a few hours ago, but I couldn't mark the item as delivered myself - I had to wait for the tracking to update. Is that normal?