What does 'ground' look like on a breadboard?
I remember having similar confusion when first introduced to circuits. There is really not much to it..

The grounds on the left and right need to be connected together. In schematics, they are often split, for convenience and clarity.

For the 9V battery, the negative terminal would typically be used as ground. However, you could also connect two batteries in series and use the mid-point as ground to get -9V to +9V supply. In other words, ground can be anything you choose, it is just a "reference point".



Image source