Your homepage is the first page visitors will see when they arrive at your website. By default, the homepage will be the page that also displays all of your posts, beginning with the most recent.
To customize how your homepage looks, including its layout, colors, enabling/disabling the sidebar, etc., navigate to WordPress Dashboard > Appearance > Customize
Under the various drop-down tabs on the left of this screen, you'll find loads of ways to customize your homepage & website in general. For example, within the "General Settings" tab, you can choose your homepage's post layout and enable/disable the sidebar.
Be sure to explore the various options within this Customizer section. The live preview on the right will show you a preview of how each adjustment will visually affect your site.