Answer: Firstly, we must draw the line y=1 onto the graph. Then, you can either choose to use tracing paper or, if you’re confident without it, just go right into the reflection.
If you’re using tracing paper, you should firstly trace over the shape and the mirror line. Then, flip over the tracing paper, and line up perfectly the mirror line on the page with the one on the tracing paper such that the trace of the shape is on the opposite side of the line to the original shape.
Then, the trace of the shape is the result of the reflection. Draw that shape onto the original axes, mark it with a C and you should get the resulting picture below.