You might need a web developer to install Craft and Craft Commerce 'locally' (on your computer), using a testing domain such at craftcommercedemo.dev
Using the '.dev' TLD will allow you to unlock Craft Pro and Craft Commerce so that you can see and test all of the CraftCMS + Commerce features.
Both Craft and Craft Commerce come with a set of template files, allowing you to interact with the site in the same way a regular visitor would (from the front end).
As a starting point, check out XAMPP (if you use a PC) or MAMP (if you use a Mac)
The above facilitates local Apache web server, plus MySQL database which will allow you to run Craft on your computer in the same way as you would on a real web server.
If you need a developer, check out this list of Craft Professionals...
Hope that helps