Excel 2007 : How to do a Data Fitting?

Hello everyone
I want your help in Fitting Data in Excel

i have two columns of data , i want to know the equation of the data in order to do a data fitting

can you help me in telling me :
1- how to know the equation from the sheet
2- how to do a data fitting

i attached a sample data , i want the data fitting to be between Ƞav(cP) and T(C°)

thank you in advance :D