How to use the Hodrick-Prescott (HP) filter to analyse GDP and its trend

I want to use the HP filter to analyse real quarterly GDP from the early fifties to today. The dataset I was thinking of using is available here: DataSet Line1 1951.I-2011.II

And here is the m-file for the HP filter that I wish to use: hpfilter.m

The problem is that I am extremely lost with just how to set it up. I was able to add the hpfilter.m file to the Matlab path. I also imported the dataset above into an excel spreadsheet, and added an additional column for the natural log of the GDP values (essentially, I want to work with the natural log values, and not the raw data). I was then able to load the dataset into matlab.

But I am extremely confused about how to proceed beyond this. Any help would be very much appreciated!