Analytics plugin not tracking

Hi everybody

This is probably a simple thing but, I installed the analytics plugin from the premium site, off course, and entered the UA-xxxxxxxxx-1 code. Now I have
MU and BP and multiple domains, but it is reporting 0 visits. I am SURE i have more than 0 visits, but maybe i needed to do more after installing. for instance the description says that I have to modify the code given by google... which I do not know where to do it.

So what needs to be done other that entering the UA code, really?