The first step is to download the extension. You need to have a valid and active developer account or you need to buy SP Booking individually. Login to your JoomShaper account. Then from your account select Downloads, next select Extenstion and browse for SP Booking or search using the search field and then click on Download button.

Now you can install the downloaded zip file to your current Joomla, like any other extensions. 

When you have a successful installation, you'll see the following screen.