How to fill up a side bar which only has a form with 3 fields?

So I have a page where left sidebar takes 25% and the actual thing takes up 75% on the right.

Basically a user would select something from the main app and fill out the form in the left side bar and submit.

The problem is there are only 3 fields for the form. I currently put them at the top of the side bar, and I have 2 buttons at the bottom of the sidebar one for submit another for reset selection.

However, this would leave almost 1/2 to 2/3 of the sidebar blank. And I don't think I can easily fill up the space with say increase font size and/or increase margin between them..

Also I am putting the label on top of each field, this makes them fill up more space vertically but then they only take 1/2 of the space horizontally.

Any suggestion on how to improve the layout in this case?