How to make the image banner narrower on fullscreen mode

[Jack-DD]

Hi I'm trying to make my image banner under my header 'narrower' so that it doesn't stretch across the whole screen and lines up with the edge of the sections. I know this may look a little silly as in theory the sides will just be white but i like the cleaner look. I'm then looking to round the corners of my image on the image banner and endure a small shadow at the top and sides so it fades out. Is there anyway i can do this as i cant work it out. (free theme only)

Thanks in advance 

[codexecom]

Please store url and Explain more about your requirement.

[Jack-DD]

Store isn't live yet. Currently with my photo on image banner which is under my header it will stretch across from one side of the screen to the other. Is there a way without editing the photo and cutting off the sides to reduce this and change the size of the image banner so that it matches the width of the sections below. (example sofaguards.com) how their image banner is at the top. 

[codexecom]

Ok Can you please tell me theme name

[Jack-DD]

Sense