How do i make the width of the body of the website bigger or a %?
How complex the answer to this one gets depends on the theme you're using. Here is an example to get you started. It's one possible way you could make the body of the Nuntius theme wider:
body.attachment #content,
#menu-secondary .wrap,
#header .wrap,
#header .wrap .header-link,
#menu-primary div,
#container,
.breadcrumbs,
#footer .wrap,
#footer #colophon,
#feature {
width: 1200px;
}
#container {
background: #fff;
}
#sidebar-primary {
background: #fafafa;
}
#content {
width: 70%;
}
#sidebar-primary {
width: 28%;
}
.hentry,
body.attachment #content .hentry,
body.attachment #comments-template,
#sidebar-primary .widget {
width: auto;
}
#sidebar-primary .widget {
min-width: 90%;
}
Note that I removed the shaded line between the content and the sidebar by setting the #container background to white and the #sidebar-primary background color to a very light gray in this example. That's because the shaded separator and sidebar background color are setup in an image in the Nuntius theme:
http://s1.wp.com/wp-content/themes/pub/nuntius/images/bg-container.png
The downside to using color codes for the backgrounds in this case is that the sidebar color will look cut off if the main content area is longer than the sidebar. If you wanted to get the exact same look the separator had before, you could download the bg-container.png image linked above, make a new one the same width of the final content area width you choose, upload the new image to your media library and replace the #container and #sidebar-primary background rules with this one instead:
#container {
background: url("YOUR_IMAGE_URL") repeat-y;
}
Replace YOUR_IMAGE_URL with the link to the image you uploaded to your media library.