It's hard to say without seeing the HTML code you're using currently.
But firstly you will want to make sure that the ad HTML is in its own <div></div>
If having it in its own div itself doesn't solve the problem, you may need to apply a bit of styling to it. It looks like it might need some right padding, so maybe something like this:
<div style="padding-right: 10px;">
YOUR AD CODE
</div>
That will hopefully push itself to the left a bit. Adjust the 10px to your needs. There may be other ways of achieving this.