In the Safari main menu bar choose:
Bookmarks>Add Bookmark> ✫ Favorites (in the drop-down menu).
Enter a short name, then click Add.
Then you can Click/drag the new bookmark (horizontally in the bar) to where you want it be.
You can also do it this way:
When you find a webpage that you want to bookmark, press Command+D. A drop-down window will allow you to edit some of the bookmark info (location and name) and then click the "ADD" button to add the bookmark to your favorites.
Or, when the page is open that you want to add to the "top bar" right click on the tab and select Pin Tab. To undo that action, repeat the right click and select Unpin Tab - which is obvious if you were brave enough to try it.