hyperlink as a button | WordPress.org

The easiest way is to just copy the button you already have on your site. Checking the code I can see the following button. You just need to copy and change the url

<a class="fbr-button fbr-mobile-100 fbr-mobile-100" target="_self" href="https://www.vladimirvondruska.cz/newsletter/?utm_source=vladimirvondruska.cz&amp;utm_medium=foobar&amp;utm_campaign=newsletter+signup"><span class="fbr-button-text">Přihlásit</span></a>