Get the gopro app on your phone, makes setting up a lot easier. Beyond that, mount the camera upside down – there’s a menu option to automatically invert the video but you can invert the recording in software on your computer.
As a rough guide – you should be able to put your first three fingers (not including your little finger) between your chest and the back of the camera casing. Make sure you have the harness really tight to avoid most of the vibration style wobbly video. Once you’ve got the angle sorted mark the mount at the swivel point with tipex or similar so if it gets knocked you can put it back without faffing about.
One tip I’ve seen is to set the recording mode for HD to 1440 rather than 1080. Effectively this is a 4:3 aspect ratio rather than 16:9 but it means that you can select the best bit of the resulting video and keep HD resolution. (GoPro Studio and iMovie both can do this, not sure of what Windows SW can do)