Adding contours to a plot

I am fairly new to root and I have a lot of learning to do. I’ve tried reading the documentation and I get stuck on some things. I have developed a basic macro to compare two sets of data, a typical Beta vs Momentum plotter. Here is most of it:

[code]void betamomentum_pip() {

TFile* myDat = new TFile("myfile.root");
TTree* ntuple31 = (TTree*) myDat->Get("h31");
TH2F *Th3 = new TH2F("Th3","Beta vs Momentum",250,0.0,1.5,250,0.0,1.1);
TCanvas *c = new TCanvas("c","pi_plus",600,450);


When the macro runs and I use the canvas interactions I cannot get it to display contours via the editor. What is the best way to bypass that and include it in my macro here?