Q. Can you help me create a graph in Excel for my biology lab?

Take a look at the step-by-step instructions on creating XY scatter graphs in Excel at these Websites:

Graphing with Excel:  depts.noctrl.edu/biology/resource/handbook/xl.pdf
downloaded from North Central College Biology Student Handbook

Guide to fairly good graphs with Excel:  http://udel.edu/~mcdonald/statgraph.html  
pages 274-286 in: McDonald, J.H. 2009. Handbook of Biological Statistics (2nd ed.). Sparky House Publishing, Baltimore, Maryland.

If you don't like Excel, try one of these free graphing software packages:

R - for statistical analysis and graphing:  http://www.r-project.org/

Gnuplot - graph oriented, with some computational capacities:  http://www.gnuplot.info/

GLE - graphics layout engine, allows much more than graphs:  http://glx.sourceforge.net/