In the form
y = mx + b
the constant term, b, is where the graph crosses the y-axis.
You have
y = (2/3)x - 5
This graph crosses the y-axis at -5. Start by making a dot there. Then use the slope. A slope of 2/3 means that when you go UP 2 units, you move to the RIGHT 3 units (rise over run). Start at the dot you made on the y-axis. Go up 2 units and to the right 3 units. Make another dot there--it should be at (3, -3). Then draw the line through the two dots.
This line is the graph of the equation y = (2/3)x - 5.