If it's what I think it is, and it shows up and stays up all the time, you can drag it (almost) all the way off the screen. I think there's an option to mute it. However if it comes and goes, then you'll have to drag it off each time it alarms. When you drag it off, it only stays there until the "error" no longer exists, when a new error occurs, it will pop up in the same place you're likely seeing it now.
The short answer is, I don't know how, or if there's a way to prevent it from ever showing up. I also don't know why it would be showing up if you're not gettting aircraft AHRS information from your ADSB device.