The UMA files come as Unity unitypackage format. It may be possible to decompose them with Unity into obj or fbx files that can be used in UE4, but using directly with Fuse without a ton of modification is not going to be possible.
The cleanest way for use in UE4 is to see if one of the moderators here can export the model files directly without using a Unity trick to get them. Still, it would even take the moderators a bunch of work for Fuse, so that is probably out.
If you look at the myshopify website which is the sister site to this one, there are lots of Fuse ready packages that can be used, but not the Viking as far as I can see.
Hope this helps,
-Jeff