Run Spotweb and go to Config -> Change preferences
Select the shown below Spotweb option "What shall we do with NZB files?" and enter the IP address:port of the computer where UE is running/listening.
In Edit menu->Properties->Import check "HTTP communication" and enter the same port. API key can be set only if needed.
The Spotnet folder in the UE database directory can be associated with an import group (see above image). Otherwise it will be associated with the default "Import" group.
Change the Save folder for the associated import group if needed.