You have an option to select the theme/template of your choice from the available wide collection. Choose the one that is closest to what you have imagined.
Navigation: Store Design>Themes
Here you will see all the available options.
You can either Apply theme or View Demo of the store from here.
View Demo will open the demo store in a New tab.
To apply a theme click on Apply Theme button, you will get a pop-up notification as below:
Once you click on Apply & confirm, the selected theme/template will be applied on your store.
You can now see it live on your store. Click on View store button given on the top right corner. This will open up your store in another tab.