I follow Manage your app signing keys which states "To create an upload key for new apps, follow the instructions on sign your app."
I check here under section "Use google play App signing", which redirects me to Manage your app signing keys. This link is the same as the first link so I stuck in a loop of redirects.
I check under section "Generate a key and keystore" in sign your app which again links me to Manage your app signing keys.
If I check under section "Manually sign an APK" in sign your app I see note stating I should use my upload key if I wanted to sign with google play app signing and for more information I should check Manage your app signing keys.
I have no idea where to get the upload key. I am just in a redirect loop.