2046's loop widget boosts you website prototyping.
First you have to have some dynamic sidebars defined. Some themes have them registered already, but I doubt they have them in the main content area where this loop widget meets it's intention. (Most of the templates have them only in so called sidebars, or header. Widgets are commonly are used for category listing, tag cloud, Facebook features etc.) The dynamic sidebar is a "slot" where you can put widgets with countless features.
Log in to your admin and go to Appearance>Widgets. If you don't see the Widgets item, then your template hes no sidebars defined. How to register sidebar.
What I do is, that I register sidebars at least one per logical block in the webdesign layout (template). Then using 2046's loop widget you can place the content loops anywhere you like and how many you like. You can interlace them by any other widgets. By drag & dropping the widgets into the dynamic sidebar areas you can easily define the structure of the whole website.
If your template has the most basic CSS setups then you don't have to wary. Widgets will nicely follow the actual template CSS rules and will obediently follow the predefined design. If you still needs some exceptions for this or that widget or it's element, every widget has it's own CSS "id" or "class" so you can easily bend them to your needs.
Well the widget is fairly complex. Check if the restrictions are not beating each other and also check if the content you expect there really is sortable the way you like it to be. If none of these checks works, then let me know on the forum, I'll do my best.