Download the installation file from the Download Page or with this link.
Multi-Language is packaged in a VSIX file, which is a special format for installing Visual Studio Extensions.
To install Multi-Language, either:
The VSIX Installer will open and show a progress bar for a short period. After this it will show a list of the possible products, with which the project can be used.
It will look something like the following screen shot, but will probably not show so many products.
In this case, four different versions of Visual Studio are installed on the same machine, which is unusual. If Multi-Language is already installed for a given version of Visual Studio, then this version will not appear in the list.
Select the version or versions of Visual Studio, for which you wish to install Multi-Language. By default, all supported versions are already selected.
Click on the Install button to install Multi-Language.
After a short period, a message will appear to indicate that the product has been installed.
Start Visual Studio.
If Multi-Language is installed correctly, then there will be a menu command "Multi Language" in the Tools menu.