First graph the two lines, (Horizontal line through (0,-3)) and , (Vertical line through (5,0)). Since you said the inequality signs are inclusive of equals (you should have written y>=-3 and x>=5 in this case), graph the two lines as solid lines to show inclusion of the ordered pairs forming the lines in the solution set of the equation.
Next, since neither line passes through the origin, select the point (0,0) as your test point. Substitute zero for the variable in each of the inequalities. If you have a true statement, shade in the entire half-plane on the side of the line containing the point (0,0). If the inequality is false after substituting 0, shade in the half-plane on the side of the line that does NOT contain (0,0).
The quarter-plane region where the two shaded regions overlap is the solution set of the system.