Hi Barb
Yes your ArcMap MXD map can be imported into a story map, but not directly as a file.
Story Maps are ArcGIS Online (and Portal for ArcGIS) application templates that display content in web maps, so you first have to publish the map data in your MXD from ArcMap either into ArcGIS Online (Esri's cloud), your enterprise's Portal, or your enterprise's Server. (It depends how ArcGIS is deployed where you work). That process gets your data online.
In ArcMap, choose File > Share As > Service in the wizard that appears choose the option to Publish a Service.
You can also do this from ArcGIS Pro. It's rather easier in Pro because after you have opened your MXD file up in Pro you can right-click the specific layer you want to publish and choose Share As Web Layer.
In both apps it is pretty neat because it automatically looks at your data and tells you if there are any issues or choices to make about publishing it online.
Now your data is online, the next step is to add it into a web map, either a new web map or an existing one you've already made. After you've authored your web map you are ready to put it to work in an app such as a story map app. For example in the Share dialog in the ArcGIS Online Map UI, you'll see the option to share your web map as an application, and a little gallery of the apps you can use appears, including story map apps. You can also go directly to the Story Maps website and launch our Story Map builders directly.
There are a couple of lower tech ways to get data from your MXD into a web map. These don't involve publishing your data as services and can be performed with any ArcGIS Online account level. You can take a shapefile created in ArcMap or ArcGIS Pro, zip it up into a zip file, and then upload that file directly into a web map. This supports up to 1000 features per shapefile. That's all you need for many simple datasets. Unlike publishing a service, using a shapefile doesn't carry any of the layer symbology or other properties (like scale visibility) over into the web map, so you have to define all the styling and layer properties in the web map, but the new smart mapping options make that easy. You can also upload CSV files and TXT files into web maps (if they have lat/longs or street addresses) to define point layers (i.e one point per row in the table). The main reason to do that rather just upload your points as a shapefile is if you have long descriptive text about the points in your ArcMap layer and you don't want that field(s) to be truncated down to 254 characters (which is the limit shapefiles impose).
