Extract and upload the Surplus.zip files to your server in a folder called exactly surplus. Create your MySQL user and database, the password is optional.
Next, navigate to yourdomain.com/surplus/install/ and follow the on screen instructions to install Surplus.
When you have done that, log in with the default admin credentials:
Email: [email protected]
Now you are logged in and Surplus is ready for you. The first thing you may wish to do is change your email, name and password. To do this, click the dropdown with "Admin User" in the top right and click "My Settings".
In here you can change your first and last name, your email address, and your password.