To customize your WordPress site you can install themes from a wide variety of options. There are free and paid themes. You can also install plugins that can add custom features to your site. Like a meta gallery, that adds slideshows to your page. To install these go to your dashboard and click on plugins, add new, and search for your plugin. Or on the dashboard appearance, themes, add new, and search for your desired theme.
Themes
Once you install a WordPress theme that you like it is a good idea to create a child theme of it so that you can make direct edits to the code if you wish too without actually touching the original files. It is good to have one as well because if you do an update you could lose some information you put together on your theme. You can edit your theme through the customization tool found under the appearance tab. Each theme has different ways you can edit the site. This is what makes each WordPress site so unique is you can truly edit it the way you want to. It also lets you add your own CSS if you wish to as well.
Plugins
Plugins are essentially a separate piece of software you can install on your website. Each plugin can do something different to what you want to do. There are plug ins that help with SEO like Yoast SEO. There is also Contact form 7 that can help you create a form on your website. Another good plugin would be google site kit, that lets you see how people find/interact with your site. There are countless plugins you can add to your site, but be sure not to add too many. Adding too many plugins can slow down your site and make it more vulnerable. If you find yourself not using a plugin anymore, delete it.
