What to do at first after copying Drupal 8 files to the server.

I am trying to build a website with Drupal 8: www.seniorama.one

I copied all the files from the core to the site.

When I try to continue the installation and go to the website, it tells me: The website encountered an unexpected error. Please try again later.

How can I solve this?

Drupal version: 


Source: https://www.drupal.org/taxonomy/term/1/feed