Step 1 
Place the protractor so that the origin (small hole) is over the point M. 

Step 2 
Rotate the protractor so that the base line is exactly along the line ML. 

Step 3 
Using (in this case) the inner scale, find the angle desired  here 42°. 

Step 4 
Make a mark at this angle, and remove the protractor 

Step 5 
With a ruler, draw a line from M to the mark you just made. Label this point V. 

Step 6 
Done. The line drawn makes an angle LMV with a measure of 42° 
