Creating line graph with two lines.

You did not include any of your failed attempts at creating a chart in your file, so it is difficult to see what you have done wrong.

If I were creating such a chart from this data:

1) Select columns A and B.
2) Insert the chart (I don't know if you are wanting a line or an XY scatter chart -- either seems like it would work).
3) If needed (because Excel often misinterprets what I wanted at chart creation), go into the "Select Data" dialog and remove, edit, add data series as needed.
4) Then add the second data series (also using the Select Data dialog).