You first need to get 2X + Y = 6 into slope intercept form which is y = mx+b
To do this you need to subtract 2X from both sides, giving you y = -2x + 6
Now you know your y intercept = 6 and slope is -2
Your y-intercept is a point on the y axis, in this case 6, so go up 6 and plot the point (0,6), your slope, -2 should always be thought of as a fraction
-2 as a fraction is 
so your rise is -2 and your run is 1
a rise of -2 means go down on the y-axis 2 units, and since you always run right, you move 1 unit along the x-axis, so you should now have a point at (1,4)
Plot this point and connect your two points, thus creating a graph, it should look like the one below
(