It opens full screen with its own icon — no address bar, no typing the web address, camera works the same.
You're on a computer
Seoul Sister installs on a desktop too — look for an install icon in your browser's address bar, or the browser menu → Install Seoul Sister. But it's built for your phone, and the camera features need one.
On your phone
iPhone / iPad — Safari
Android — Chrome
Already had the app and got signed out?
Delete the old icon first (press and hold it, then remove), then add it again from www.seoulsister.com using the steps above. Adding it without deleting the old one leaves the broken icon in place.
This page is always at www.seoulsister.com/install — no account needed.