We don't offer direct software updates, rather you just install a full copy of a newer version of OpenStudio, either from our main download page for quarterly releases, or from our developer page for minor (iteration) releases.
Did someone else send you the OSM file? If you create the OSM files on your own generally your OSM should be the same or older than your version of PAT. If your OSM is from an older version of OpenStudio then PAT should do the version translation of the seed model to bring it up to the current version. You can't however load a 1.8.0 OSM as a seed model in PAT 1.7.0. One case where I would expect you to see OSM files newer than your version of OpenStudio is if you run simulations on the cloud and then download a datapoint.