To install a new theme on your WordPress website, visit the admin dashboard, then select the Appearance > Themes option from the menu.
You can then select a theme to activate from the list of currently installed themes, or add a new theme by pressing the Add New button.
The first page of the themes list contains the most popular WordPress themes such as Astra and GeneratePress, as well as older default themes such as Twenty Twenty.
You can also choose to upload your own custom theme if you wish – this will only be available to your website however. If you think your custom theme is worthy enough, consider submitting it the WordPress official Themes Team for review. Your theme might just be the next best thing!