The Button Block allows you to easily add buttons with HTML links into your content.
Once you've added your content to your block, there are further options available in the Settings Sidebar. You have the choice of a number of different styles for your buttons along with selecting the button colour and the text colour.
To add or edit the text on your button, simply click on the button and type your button text. Just under the button is an input field where you can enter the URL for your button link.