How to add instructional starter page - Web App Builder or Storymaps

[MeganPrescott]

I have several interactive maps made with Web App Builder, which I've embedded into Storymaps. I'm hoping to include something like the initial pop-up in the link below (where the background is greyed and instructions are given for navigation, background information, explanations...)

NatGeo Mapmaker Interactive 

I know I could make a cascade storymap to explain navigation, and then embed that in a separate adjacent tab (tabbed storey map) before the interactive map, but I was hoping for something more streamlined. 

Does anyone know how I can approach this? Thank you 

(More information - I am hoping to embed this into 1. a web app builder-made interactive map, as well as 2. a Tour Storymap)

[XanderBakker · Accepted solution]

In Web AppBuilder you would use the Splash widget—Web AppBuilder for ArcGIS | ArcGIS 

[MeganPrescott]

Thank you Xander, this is exactly what I was hoping for.