Go to your url of your website and attach the characters
"/admin" at the end of the url.
Remember that when you signed up you got a domain. use that domain and attach the route "/admin"
Enter in your username and password
When you get to the admin page you will be presented with a login form. Enter in your username and password.
Once you have entered in your credentials correctly, you will be able to adminstration duties like uploading products
Lets say your domain is rentalsetup.com go to the url
Lets say your domain is rentals.rentalsetup.com go to the url