Hello
Considering how the Trinity template is laid out I am sorry to say this option is not available with our Trinity template. You could try adding the following to the Custom CSS field of your templates parameters however you will experience some issues if you wish to use the header slideshow option...
#header_bg {
position: fixed;
top: 0;
width: 100%;
}
#header_slide {
position: relative;
}
CiarĂ¡n