To do this will require a bit of HTML coding. This is because what you see as a button is actually a form. There are a number of posts about button positioning already. So, I encourage your to look around this forum for more information.
Here is a post regarding button page centering viewtopic.php?f=2&t=351&start=0
Here is another that is more specific to your request viewtopic.php?f=8&t=310&start=0&hilit=inline
Please let me know if you need anything else.
~ Best regards