I am adding the maps to a cascade story map but need a legend.
See this Cascade put together by John Nelson, of the Story Maps team, on how to incoporate legends in a narrative way. https://nation.maps.arcgis.com/apps/Cascade/index.html?appid=954145df6cf84e2d8bbea996438c99fb
Are you working with Web App Builder?
You may refer Legend widget—Web AppBuilder for ArcGIS | ArcGIS .
I hope this helps!
Retrieving data ...