The themes you linked in your questions are fully populated with posts, menus, slider content and widgets.
After a fresh installation of WordPress you have 1 post, 1 page, 1 comment. So your site won't look even close to what these demo's show because you don't have enough content.
You will need to create a decent amount of posts with featured images (those are the images that appear associated with each post, the theme should provide a field to add them to the post).
You might need to add info to a custom post type called slider depending on how the template is designed to add the slider content.
You will need to add widgets to get the content they are showing in their footers.
The social icons might need to be enabled and info must be added so they work towards your own links.
The question you made is too vague for me to know if I hit the point, but given it's vagueness I would suggest some beginner tutorials on how to get some of this stuff done.
I'll suggest this tutorial, there's a free trial, but I'm not sure how far it'll let you go into the course. On the other hand you can search the topics that are on the link in youtube and get some good tutorials as well. That might help you move a bit further into WordPress and get some juicier questions for us.