Some themes come with One Click Demo Import feature. You can import demo contents with one click. Theme settings, pages, menus, posts, categories, post types, taxonomies, widgets and other features import to your site. If your theme support the feature, you can apply this method.
Firstly, go to Appearance > Import Demo Content from admin panel menu.
If your theme have many demo, choose a demo and click on the Import button else your theme have one demo(Or many homepages) click on Import Demo Data.
You will see the notification after import. You can use and customize your theme.