There are two ways:
1.) If your Joomla 1.53 is a new installation (you have no content) then you can delete it. After them you install the Quickstart package. So your side looks 100% as the Demo and all extensions are automatically installed.
I think its the best way.
2.) The second way If you have content and you didn´t want to delete your Joomla installation,is to go to the download section. Download the JA Erica 1.5 extensions.zip to your Desktop. Then doubleclick on the folder and extract it.
Now you have a folder with two moduls (janewslight zip and login zip ). Go to backend and there you can install both moduls. Don´t forget to enable them and config the positions. You find them in the describtion of JA Erica.