1) Open http://resharper-plugins.jetbrains.com/packages in a browser;
2) Log in to a site;
3) Find a plugin e.g. http://resharper-plugins.jetbrains.com/packages/JetBrains.AngularJS/ (pay attention, that there may be two versions of a plugin - one for R# 8.x and one for R# 10.x/2016.x);
4) In "Versions" tab, select a plugin version which covers installed R# build;
5) If you logged in, there will be a Download link;
6) Hit Download link and download the nuget package;
7) Put it to any local folder;
8) Specify such folder here "ReSharper | Options | Environment | Extension Manager | Add" and uncheck ".NET Products Gallery" checkbox;
9) Run "ReSharper | Extension Manager" and install the plugin which appears there.
Hint: if you use IE11 and it downloads *.zip file instead of *.nupkg, just change the file extension from "zip" to "nupkg".