First plot the y-intercept.
The equation is in the form: y = mx + b where b is the y-intercept. So when x = 0, y = -5.
(0, -5)
Then choose any other x value to obtain the y value of that coordinate. For example, plug x = 2 in the equation.
y = -1/2x - 5
y = -1/2(2) - 5
y = -6
So a second point can be:
(2, -6)
Plotting these two points should make a linear graph as desired. I attached a picture of where the two points should be as reference.