1. Unfortunately, it is not possible to install the Quickstart package inside an existing Joomla installation via the Extension Manager, because the Quickstart also includes the Joomla! CMS itself. This package is strictly for use with a new Joomla! installation to provide you with a duplicate of our demo for that particular template.
   
2. You can install Quickstart just like a typical Joomla 3.x installation process (step by step).
3. Unzip Quickstart package to get separate folders and files before sending to server.
4. Please do not use "admin" as a your default Super Admin Username (!). Use something more unique during installation process (security reasons!).
5. In most cases we suggest to use a new/fresh database (MySQL 5+) for all QS installations.

Please also read our article -> I’ve installed Quickstart, So what’s next?

The Manual template installation is preferred if you just want to install the template to an existing website which already has some content. However, keep in mind that when you install the template to an existing website, you will also have to reconfigure used modules because the new template has different module positions. But we always suggest to install QuickStart on temporary location, like sub-domain, to check all settings and demo content.

The Quickstart installation problems

Because QS includes many extensions and their settings it requests good PHP settings. Check mentioned above technical requirements.

If during QuickStart installation on localhost you have never ending installation, please check your PHP settings (suggested values above) and if those settings will not help please make small customization:

• Open in your text editor the following files: installation\sql\mysql\joomla.sql and installation\sql\mysql\sample_data.sql
• Find all instances of ENGINE=InnoDB and change/replace to ENGINE=MyIsam
• Now return in your installation procedure one step back and try again.
• Use MySQL in choose field not MySQLi if you still have problems with database step.