Sorry, but there is no real installator for now.
1. If you downloaded XamlLocalizerBinaries.zip, it may be blocked by Windows.
That's why right click on it in Windows Explorer, select Properties and then click Unblock.
2. To install plug-in please copy content of correspondent folder into folder
<MyDocuments>\Visual Studio 2008\Addins\
<MyDocuments>\Visual Studio 2010\Addins\
(If folder "Addins" doesn't exist there, simply create it.)
3. Then restart VS.
If addin didn't appear in Tools menu, then please open "Tools - Addin Manager..." and mark checkbox for "Xaml Localizer".
Known installation issue:
Addin assemblies may be blocked by system, because they originated from internet, and VS will show error #80131515.
As a workaround you can in Windows Explorer click Properties of each addin .dll and click "Unblock".
You may change behavior of addin, so it will fit needs of your partucular project.
On the page
How to tune addin using XamlParseInfo.xml
important elements of configuration file are described.