Change Frontpage Bootstrap Layout

I am still totally new to Drupal. I have installed Drupal 8.3.2 so the latest Version. I have installed the Bootstrap Theme and activated it. I now want the Front Page to look different to the Layout of the other Pages meaning I would like:

A image slider, below that 3 Boxes with Content while 1 will be Latest News and 2 with static content below that a full width box then a Gallery with multiple images in 2 rows.

I have copied and pasted page.html.twig from themesbootstraptemplatessystempage.html.twig into the same folder and renamed the file to page–front.html.twig. I tested it and the new file does get used.

Now my question what do I do now with the file? Do I make the changes directly in page–front.html.twig or do I need to go through the Admin Center? The Front page shows right now “No front page content has been created yet.” Do I need to create a Page and assign this to the Front? I have got the Region Content and suppose that is where all my boxes should go, but how would I do that? I am still not sure how to do things the “Drupal way”.

Thank you very much for any hint.

Drupal version: