Choose the first graph on the second row as that fits your criteria for this graph best.
Enter data in cells in column a & column b. The first column should be the year, the population is shown for. You will need to type an apostrophe so Excel knows you are putting in a year not a number. Then, put the population amounts in column b.
Note that the independent variable is placed in the first column while the dependent variable is placed in the second column. The headers at the top of each column are not necessary, but they do help identify the variables.
With the data shown above highlighted, start the Chart Wizard from the toolbar:
If the Chart Wizard is not visible on the toolbar, you can also choose Insert > Chart..
Check to see that your data is in columns on your spreadsheet.. Label the axis to show the year and population.
You may want to change the colors on the graph to reflect the different years. This will make your legend change.