How do u graph linear equations like this where it's just y=-5x ? plz explain

Calculate the y value for a bunch of x values.

E.g. x=0: y=-5*0 = 0, plot the point (0,0)
x=1: y=-5*1=-5, plot the point (1,-5)

repeat the process until you are confident to draw a smooth line through it. For straight lines two points suffice. In this example I'd choose them sufficiently far apart, like x=-4 and x=+4.