How to drag and move icons in the Gnome-shell favourites bar?
Click with the left mouse button, drag a bit to the right, find the spot you want to rearrange it to and leave the mouse button
Dont mind the blue, its caused by the screencast tool
If you can't move the icon by dragging it with the mouse then install cursor theme:
sudo apt-get install oxygen-cursor-theme
and go to Tweak Tool,
change the cursor theme and then it should work!
An alternative way is to click on "activities" in the top left corner, then drag and drop the starter icons just as you like.