My live website is not user-friendly, and I'm considering to use a new template. I bought a template, but how can I use the new template for the same content with some modification? If I use new template, will it be harmful for SEO? If there is no problem with SEO then I was thinking to modify the website in local server and when it is ready then will upload to live server. will it work this way?
First of all, you should absolutely work on a copy of your website when doing major layout changes. I recommend using Akeeba Backup, and restore a copy on your local server.
Templates are installed just like any other extension (through Extensions -> Extension Manager). Once installed, you can set it as default from Extensions -> Template manager by clicking the star next to the new template. You can also preview your template by adding
?template=template_name to your URL (e.g. http://example.com/index.php?template=Beez3).
A template does not affect your content. You should however be aware that different templates might use different module positions, especially if they are from different template developers. That means you probably have to change the position of all your modules to make the site look right. For example, the sidebars has many different names depending on your template, I've seen left & right, sidebar1 & sidebar2, side-a & side-b etc. It's possible that some of the positions in your current template are unavailable in the new one.
In addition, modules often use Module Class suffixes in order to obtain a certain layout:
This is also template dependent.
The best way to find the available module positions is to visit the template developers website. The template demos usually has a menu item called "Module positions" (or similar) that shows available positions and suffixes.
At the end, installing a new template is not overly difficult, but it will take some time to make it look right with your existing articles and modules.
Yes, a new template could significantly affect your SEO, either negatively or positively. Not only do you have to consider document semantics and elements like microdata but you must also know that performance and mobile-friendliness is also is a metric considered by search engines.
Will a template that uses semantic sectioning elements, Landmark roles and microdata perform better in SEO terms than one that doesn't? Yes.
Will a faster template perform better in SEO terms than a slow one. Yes.
Consider accessibility and performance as key criteria when choosing a template.
Step 1: Log into your Joomla administrative dashboard.
Step 2: In the top menu, click Extensions and then click Template Manager.
Step 3: You will see two types of Joomla templates, Site and Administrator.
In the list of templates, click the hollow star next to the Site Template that you would like to activate your new uploaded template. You will then receive the following message:
You get successful message!
Message Default style successfully set