I would recommend installing the LoadRunner Community Edition software which would provide a full install that includes VuGen and it would provide the Load Generator Software. Maintenance is much easier for all your machines where VuGen would be installed by itself.
If you wanted to Install just Vugen. You will need to download the full LoadRunner package as this is the only package that has VuGen (Standalone). You would need to download the ''LR 12.53- Full Installer package'' and select VuGen to install.
For Standalone Load Generator only, you would need to download the ''HP LR 12.53 CE Standalone Applications'' and install the Standalone Load Generator software.
Note that it is very important to ensure all of your LoadRunner components and software are the same version and apply the appropriate patches. Different versions can and will cause issues.