Hi All...I am a Bootstrap newbie AND a jsbin newbie so hopefully this goes well LOL

I want to put a jpg into the Jumbotron area of my page, adjusting the opacity so that the text that is contained in the header shows up.

How do I know what size to make the jpg in order for it to fit in the area I want it to fit in? I'm using a picture of the Seattle skyline but the picture is so huge that only the very tippy top of the picture even shows up...so the picture is going to have to be resized super small to fit....make sense? How do I know what size to resize it to in order for it to fit? (I resize with Paint)

So I created a jsbin account and am going to attempt to put all my code there...if someone could help me I'd appreciate it! (by the way the page is no where near done LOL)

Unsure how to get the image to those who want to help though...or is that even necessary? I just want to know how to know what size to make my image so that it fits within the jumbotron...thanks!

http://jsbin.com/figula/1/edit?html,css,js,output