it's pretty straight foward :
1) To move around the apps in the dock, click and hold the application you want to move ... and move.
2) To add an application or w/e to the dock just drag 'n drop it to the dock.
3) To remove an aps from the dock, right click on the app you want to remove (to right click, either ctrl + click or 2 fingers click on the app) and select remove.
In the Apple menu, top left, you'll also find a Dock section. You can customize a bit the dock there.
Hope I helped.