Help Fixed Image Background : Help with adjusting width?

[ParadoxiiNight]

So, I want to make the box with the picture background and 'another title' in it less wide, but I don't know how to. Any help would be appreciated.

Mini title thing (don't worry bout it)

Another title​

[centerblock=100][border=1px solid #F8F8FF][bg=#000000][font=Bellota]Mini title thing (don't worry bout it)[/font]


[div=background:url('https://www.rpnation.com/gallery/abandoned-lab.42529/full')fixed;background-size:cover;border:1px #F8F8FF solid;color: #F8F8FF;padding:15px;]

[font=Cinzel]Another title[/font]

[/div]

[/bg][/border][/centerblock]

 

[Alteras]

In your div, put in width: 70%; text-align: center; margin: 0 auto;