Whether you're sending your stream to a club promoter, sharing with friends online or just analysing your progress, setting your audio levels correctly is really important.
When previewing your stream you will be able to see audio signal from the mixer to the tablet via the audio levels peak meter. Ideally you want this to be hitting between -10db and 0-db to avoid any unwanted clipping or distortion.
If the signal running from the mixer is too hot then you will need to turn down the TRIM controls on the channels that are being used (circled in green). Turning down the MASTER volume will not control the db level of the stream, only how loud the speakers are in your room.
If you aren't getting a reading into the tablet then this is because there is no cable running out of the mixer. You need to make sure there is an AUX cable running from the REC OUT (labelled in orange).