Only Template Installation
Using Joomla! features, you can easily change your website's template at any time. Changing your template lets you explore a variety of design styles and color combinations, which can completely change the look and feel of your website. In this tutorial we will teach you how to install a new Joomla! template and set it as default for your website.
The first thing you need to do is to download the new Joomla template you're willing to use for your site on your local disc.
If your site have content already you can install template and modules only. Quickstart is good only for new websites because it contain Joomla package itself.
Before installation, check the compatibility whether the downloaded version of template is compatible with your version of Joomla.
Once you have your Joomla template downloaded on your computer, login to the administrative area of your Joomla website and upload the template through the Extension Manager (Extensions -> Extension Manager).

Extension Manager
Click on Browse button and select the template bundle archive you downloaded earlier. Finally, click on upload & install. After installing the template, you should receive a message "Installing template was successful!". At this point, you have successfully installed a new Joomla 3.x template.
Please note that this has not activated your new template, you still need to do this if you want to use this design.
Once the template is installed in your Joomla 3 system, you need to make it default for your website so your pages get the new design. First, you need to go to Extensions -> Template Manager. Now select the template checkbox near its name and click on Make Default.
You can also assign new template for specific subpages (menu items) only - using Assign option inside settings.

Template Manager
Last modified 4yr ago