Actually Both Smederna-Eskilstuna, Rospiggarna- Hallstavik and vargarna-Norrköpingare Easy to get to.
Since you are flying with Ryan Air you will probably land on Stockholm-Skavsta (Nyköping) whichs about 100km south of Stockholm. Eskilstuna is about 80Km north of Nyköping and you get there by travelling with the "Flybussarna" (Airport coaches) (directroute). for Hallstavik, Airport coaches or train to Stockholm and then bus or train to Hallstavik. Bus/train To Norrköping.