how to use excel

you create formulas according to your need of the mathematical calculus you need.
=sum(F13+F8) this all depends on the types of results you want
the graphs describe the information you enter in a visual way an there are many types of graphs like: Bar Graph, Line Graph, Pie Graph, etc. you use all this types of graphs in order to show visually what your data is about and it is easier to see data than read data.
http://www.youtube.com/watch?v=jLW1A7j7r3Y