Select the area you want the lines to show, then right click and select "Format Cells". Click on "Border", then select the thin, solid line. There will be a white box that says "text", click around the border of that and it will turn on the lines.
You can also go to File>Print. When it comes up and gives you the printer options (i.e. choose a printer and all that), click "Page Setup". Once there you can go to the "Sheet" tab, and make sure the "Gridlines" box is check marked. This will print the grid lines for the entire page regardless of what you selected.