Luckily for you, we studied cross-section last year for school. I hope this helps!
1. Draw a line between the two points on the map.
2. Place a piece of paper along the line and make marks wherever contour lines appear.
3. At each mark on your paper, fill in the height of the contour line
4. On a clean sheet of paper, rule a line the length of the distance between the two points.
5. Create a graph with suitable intervals.
6. Moving along your graph horizontally, match up your heights of the contours with the corresponding height in the y axis.
7. Join the dots.
Good Luck!