Pendulum = Import["http://www1.lasalle.edu/~blum/c152wks/Pendulum.csv", HeaderLines->1]

ListPlot[Pendulum]

Show[Out[2], AxesLabel-> {HoldForm[length (cm)],HoldForm[Period (s)]}, 
PlotLabel->HoldForm[Pendulum Data]]

pendFit=FindFit[Pendulum, a*x^n,{a,n},x]

Plot[0.210807*x^0.488666,{x,20,105}]

Show[Out[3],Out[5],Epilog->Inset[Framed[Style["y=0.2108 x^0.4887"],
Background->LightBlue],{50,1}]]