WebShots does not require any data beyond that already in your analysis. The WebShots wizard will allow you to specify:
Up to 5 scenarios you want to display
Up to 5 assumptions you want users to be able to vary
Up to 5 discrete settings for each variable assumption (in addition to its default setting)
It will also let you set various other preferences for what you want to display.
Assumption values that are not varied in your WebShots display will be fixed at the values they have when you start the WebShots wizard, even if they are variable assumptions. Therefore, you should
Set other variable assumptions to the values you want to use before starting the wizard
Before starting the WebShots wizard you should set up your layers the way you want them to appear in the WebShots and set the other variable assumptions to the values you want to use. Make sure to consider which layers are on or off and what map symbology you are using, because your viewer will not be able to change these settings.
Note that charts will display in a scrollable window, just as they do on your screen. You may want to consider using Saved Views.