You can do a soundcheck at any time.
Go to your channel and (assuming you have already scheduled a show) click on the big orange "Go to Broadcaster" icon.
Choose if you're going to broadcast with Web, iOS, or RTMP, then switch to "Test" mode and start broadcasting. No one will be able to see it on your channel. Click the "Test URL" link below the broadcaster and you'll be able to see your test stream in real time. You can also send this link to a friend.
We recommend using headphones so you can monitor in real time while you soundcheck.
Notes: Make sure to select the correct inputs for your audio and video. This may require going into your System Preferences (Mac) or Control Panel (PC) to select the inputs in your computer settings. You will also have to allow Flash Player to access your inputs. Right-click on the broadcaster video and select "Settings". Make sure you have selected "Allow" in the Privacy tab and the correct microphone and camera inputs in the Microphone and Camera tabs.