Changing homepage picture

I’m trying to change the main photo on the homepage. I’ve gone to Theme Options and put in the html code for the image I want to use and I get an error message. I’m sure I’ve just typed something wrong but I’m new to this and I don’t know what it is. Here is what I typed:

<img class='aligncenter' src='/inc/img/name-of-image.JPG' width='940' height='420' alt="/>

If you could help I’d appreciate it!