How to access staging area

I created a staging site so I now have a production URL (https://[accountname].wpengine.com/ and a staging URL (https://[accountname].staging.wpengine.com/.

I know how to access the staging staging site’s database via PHPMyAdmin and SFTP, but how do I access the staging area via the WP admin so I can test changes?

The instructions at https://wpengine.com/support/staging/ say:

“You can access the staging area by simply logging into the admin for your live site, i.e.: https://installname.wpengine.com/wp-admin.”

But it doesn’t tell you where to go next. In the admin, I’m aware of the staging tab where you can copy the staging to live and vice versa, but how do you actually makes changes to the staging site when you’re logged into the admin for your live site?