OK. Now that you already know what a theme is and how it works, it’s time to get our hands dirty. Let's see …

How to install and manage themes on WordPress?

Just like almost anything else in WordPress, installing a new theme is extremely easy. Basically, you have two options:

• to install a free theme from the Wolrdpress theme directory

• to install a free or paid theme using a downloaded archive file from your computer

So, let’s start with the most obvious option …

Installing a theme from the WordPress theme directory

As I said, if you want a well-tested and secure free WordPress theme for your site, the WordPress theme directory is always a safe way to go. Let’s see how it works …
At this point if you click the “Customize” toolbar button in the front-end area, you’ll be taken to the customizer. As you can see, my current theme is called “Twenty Seventeen”:

Usually, you have two more – pre-installed – themes: “Twenty Sixteen” and “Twenty Fifteen”. As you can guess, these themes have been named after different years. Any newly installed WordPress application comes with a set of default themes that have been named after the year they were released, so right now the latest default theme is “Twenty Seventeen”.

If you click the “Change” button, you’ll be able to see all the available pre-installed themes and the “Live Preview” buttons will allow you to see what your site looks like with “Twenty Fifteen” or “Twenty Seventeen”. But, don’t forget, these are just previews generated by your own browser (these changes aren’t visible on your live website). If you want to actually change the current active theme, you’ll have to hit the “Activate & Publish” button:

But right now we have a different goal: to install a new theme from the WordPress directory. So, let’s do it …

Go to the back-end area, select “Appearance -> Themes” and click the “WordPress.org Themes” button:

And there it is … the WordPress theme directory.

Now here’s a quick tip … Before you start browsing click the “Feature Filter” button to bring up the filter panel where you can start narrowing your options according to your needs:

When you’re done just hit the “Apply Filters” button.

And here are the available themes according to my filters:

I am going to choose a theme called “Gaukingo”. Of course, you can choose whatever you want …

If you hover your mouse over the selected theme, you’ll see the aforementioned “Preview” and “Install” buttons:

If you click the “Preview” button you’ll get access to a so-called test preview that will be generated in your browser using the demo content included in the given theme.

If you click the “Install” button, the theme will be downloaded and installed into your website: