If you have a graph there's a cross and the line going up and down is the y-axis. The line going left to right is the x axis. when someone gives you a line it'll look like this -----> (2,4) this means you need to mark 2 on the x axis, and 4 on the y axis. A line is always (x,y) so you'd plot 2 on the x axis and 4 on the y axis and draw a line.
for the y-intercept one, a y intercept is a number where a line goes thru the y axis, therefore the -2 would be on the y axis and it's where u start, so put a point on -2. Then the slope is -2 so put that like this -2/1 that means go down 2 times and go to the right 1 time, so you'd do that
it's kinda hard for me to explain but i hope this helped!