To animate a line graph in PowerPoint, you need to open the slide, draw the Graph add the labels and then animate the graph as explained here.

How to Make a Line Plot in PowerPoint. If you need a line chart, Microsoft PowerPoint 2010 can help you plot your line graph on any of the slides that make up your presentation.

Learn how to create a Timeline in PowerPoint for the Web, select different styles or change the color for a PowerPoint Timeline graph.