Well the answer is yes and no 
parts that have been accepted into Fritzing are in the core library and will update in to your machine automatically. Parts that are either waiting to be approved and installed are often on github but won't yet automatically download and some folks have parts on github and haven't requested they be included. For those parts you can down load them to your machine and then import them with file->open. When imported they will appear in the mine area of the parts window but are stored in your space and thus won't overwrite the core parts.
As well there is the parts submit portion of the forums here which also have parts you can download, but from the question I expect the part you want is on github so you need to download it from there and then import it. Note some of the contributed parts are in forks off the official repository, for them you have to select the appropriate fork on github and download from there. I mention this because I wanted such a part and it took me a while to understand that I was trying to load the official repository (which was pointless because I already had it) and needed in fact to navigate to the forks in the top of the tool bar to the correct user's fork of the main repository. At that point I could download and import only his new parts not the entire
repository as I had been trying to do
Peter Van Epp