Jelling is home to the Danish national museum of the Viking era as well as the home of Herald Bluetooth (after whom the bluetooth technology was named).
Kongernes Jelling is a museum dedicated to the Viking kings. There is a fantastic visitor and experience center in the middle of the monument complex around Jelling Church. At the Experience Center you can learn about Viking kings Gorm and Harald, their rune-stones, the huge ship-setting and the gigantic palisade which was built over a thousand years ago. The museum is small and highly interactive. Admission is free.
Next to the museum is Jelling church and the location of the burial mound. Here, the Kings Gorm the Old and Harold Bluetooth erected their runestones and built the monuments in the years from around 950 to 970 AD.
It is incredible to see the runestones in their natural outdoor setting right where the Viking kings left them (now encased in glass to protect them from the elements). In these stones, Herald Bluetooth moves his society from the Viking stories and legends to embrace Christianity -- to create a connection between the old ways and the new ways. Really great site!
It is pretty straightforward to get from Aarhus to Jelling via train. While you may need to change trains, the stations are well marked. Note that the station at Jelling does not have a fully staffed ticket office (no one may be there to sell tickets). There is a kiosk to buy tickets. Be sure to have exact change or the kind of credit cards that work in European ticket kiosks.
Visit the Kongernes Jelling online: https://en.natmus.dk/museums-and-palaces/kongernes-jelling-home-of-the-viking-kings/