How do I… · Premiere Pro
Vertical, 1080×1920, H.264. The sequence has to be vertical too — exporting a wide sequence at a tall size just adds bars.
Keep titles and faces away from the outer edges — the app puts its own interface over the bottom quarter and the right-hand side of the frame. Audio: AAC, 320 kbps, 48 kHz. If the upload looks softer than your export, that is the platform re-encoding, and the fix is a slightly higher bitrate rather than a bigger frame.
This page is written by the people who make Open Portal: press Ctrl+Shift+O, box any part of your screen, and ask about it. Premiere Pro included — it works in every app, because it reads pixels rather than plugging into anything.
Faster than searching: box the part of your screen you cannot work out and ask about it directly — in Premiere Pro or anywhere else. Answers arrive where you drew the box.