To change the theme (appearance) of a WordPress website, first check which theme you currently have installed, by clicking on the left side menu ‘Appearance’, then under ‘Appearance’ click ‘Themes’. in the below image you will see that the ‘Twenty Sixteen’ theme is installed.
To decide which theme you would prefer, click WordPress.org/Themes so that a new page will open with all free themes available to install.
When you hover (place mouse) on top of a theme, click the ‘More info’ link to see when the theme was updated, how many active installs it has, what are the average ratings and to read the description so that it helps you decide how popular and good the theme is.
To check how the theme looks, click on ‘Preview’. Alternatively, you can view available themes by clicking ‘Feature Filter’ so you can find a more specific theme for your needs. When you finally decide which theme to use, copy the theme’s title, then go to your website dashboard (www.yourdomain.com/wp-admin), on the left side menu click ‘Appearance’, then under ‘Appearance’ click ‘Themes’, click ‘Add New’ and in the ‘Search bar’ (top right) paste or type the theme title you want and press enter, then place mouse on the theme, click ‘Install’ and then click ‘Activate’. You can change theme anytime in the future.