Here is a guide how to install a Joomla template into an existing Joomla website. When you download a Joomla template from CmsBold, there is a ZIP file for template package for example: bold_material.zip. Basically, installing this Joomla 3.x template process will include 3 simple steps as below.
Steps to install a Joomla template package:
Step 1. Log into the Administrator Panel of your Joomla 3.x website and navigate to the Joomla Installer: Extensions > Manage > Install
Step 2. Under 'Upload Package File' tab in extensions manager screen, click 'Choose File' button and browse to bold_material.zip file on your computer. Just select it and click 'Upload & Install' button. Within a few seconds, you will received a message for successful installation.
Step 3. Now setup installed template so your website will be based on it.
Just navigate to Extensions > Templates > the system will show a list of installed templates on your Joomla website. Keep in mind that you can install many templates into your site as you wish, how to use templates on your site will base on this assignment section.
Select a template and click the 'Default' icon at the top left of the page or click on star icon along with template name set it as Default template:
In case that you want to have styles of installed template in certain pages, just click on the template name to edit > navigate to 'Menu Assignment' tab and select associated menu items
Now if you navigate to front-end of your website, you should see the its style based on installed template.