Go to Pages > Add new and create a New page. Give it a name e.g. “Home” and from the Page Attributes panel on the right set the template to Homepage, as the following screenshot shows. Hit the Publish button on the top right.
When you are done, you should be ready to click the Publish button once again.
Go to Settings > Reading and from the first set of radio buttons, check the “A Static page” and from the front page dropdown select the page you have created, like at the screenshot below. Click Save and you are good to go.
In order to create the layout structure of the homepage, you need to add Section Widgets to the "Widget Sections" widget panel, under Appearance > Widgets. More details at the related section of the documentation.