Fitting different function on one histogram

Hello; im a new user of ROOT (4 weeks and counting) and so far everything is great (if not a bit frustrating, due to my lack of programming experience)

I was wondering how would I go around fitting different functions for a histogram? I want to fit both gaussian and a poisson on a normalized freq. histogram but I don’t have any clue how to go through with this.

ROOT User’s Guide - Chapter 5. Fitting Histograms
ROOT Tutorials - Fitting tutorials