How to apply patch file to views module in Drupal 7
If it is a standard Drupal patch, you use a program named git (part of ambience in most Gnu/Linux configurations) to apply it.  The correct procedure is to first clone the newest released version of the project, apply the patch, then install the patched version in the views folder.  If the patch file is named views-bugfix.patch you download it, and then:

git clone --recursive --branch 7.x-3.x http://git.drupal.org/project/views.git
git apply -v views-bugfix.patch


In some cases, the patch is not for the released branch, but some other branch (this will be mentioned along with the patch).  In that case you need to clone this branch instead.

Source for this info.

If you're stuck in a Microsoft environment and don't have git here is something that may help you: Patching in Windows (haven't tested this myself - I don't do windows.)