Yes, you can change your WordPress theme at any time. Another big benefit of switching to WordPress.org is that you get additional customization options and a larger collection of themes to choose from.
In your WordPress admin sidebar, click on the Appearance Menu dropdown and select ‘Themes’ to install a theme.
We have hand-picked some of the best themes to help users avoid choice paralysis. See our guide on the best free blog themes and best multi-purpose themes for WordPress.
You may also want to see our guide on how to properly change a WordPress theme.