Creating a Rotor Item
To create a new Rotor Item, go to the Create Rotor Item page (from the Create content menu). From there, enter a "Tab Text" title for the Rotor Item (even though, at this point, it won't be displayed anywhere but the "View All Rotor Items" page). You can (and in most cases will want to) add a link to a content item that the image will link to when clicked. Note that this can be either an internal (within the main site) link to an existing content item or an external link. Most links will likely be internal, either to a product page or an announcement page (rather than linking directly to a "service" itself).
Under Rotor Image, choose and upload an image using the appropriate fields. Some image specifications are listed below. You can add Alt Text and Title Text if you wish. The content field is optional, but I usually fill it in with the text from the image in case the image doesn't work for some reason. All the rest of the settings are good at their default. Do not publish these nodes to the front page. They will be published (and thus appear in the slideshow) by default.
Try to make the banner item you want to appear into an image with the dimensions 875x280. That way, you can position and lay out your banner however you want and know it will display that way in the slideshow.
The basic premise behind the slideshow is to provide short snippets of information at a glance so visitors are attracted to the site and (more importantly) its content. Thus images should be appealing to the eye, informative, and easy to read quickly. They'll most likely contain a small amount of text (certainly no more than 2 moderate-length sentences worth).
Controlling Slideshow Items
The slideshow only shows published Rotor Items. Thus, setting a Rotor Item node as "Published" or "Unpublished" determines if it will appear in the slideshow. To make an old/outdated/no longer useful Rotor Item no longer appear, simply edit the node and Unpublish it.
In terms of number of "active" (that is, published) Rotor Items, there isn't really much of a need for more than 5. More than 5 items would likely just confuse users and get in the way. 3 to 5 items is most ideal.
Note that if there are no published Rotor Items, the slideshow will cease to display. (This should be fairly obvious, because at that point, there will be no images to display).