To install the gallery, you need to go to

User/Library/Application Support/Adobe/Lightroom on OS X,
C:\Documents and Settings\User\Application Data\Adobe\Lightroom on XP-Note that Application Data is a hidden folder,
C:\Users\User\AppData\Roaming\Adobe\Lightroom\ on Vista,

where User is the name you log in with. Look for a folder called Web Galleries within. If it’s not there, create it yourself. Unzip the file into this folder and restart Lightroom.
The new Gallery will apppear in the Right Hand Panel, in the Galleries Panel in LR1 and the Engines Panel in LR2.
In LR2, you can also open the Preferances and click ‘Show Lightroom Presets folder’ in the Presets section.

I recommend that you create an alias/shortcut to this Lightroom folder for future use.

Update
If you wish to comment on a gallery, can you please do so on the the gallery post, or the associated Lightroom Forum post? Thank you.