To the venue
The closest stop for public transport is Bislett. It is available by bus 21 and 26 as well as tram 18 and 17. If you live at one of the recommended hotels, the tram will be the best option. Download the app “Ruter” to buy digital tickets for all public transport (tram, bus, metro) or buy a single-use ticket at Narvesen or 7-Eleven.
Depending on the weather conditions (keep in mind it will be winter) you can always walk in under 15 minutes from the hotel to the venue.
There is always the option to take a Bolt/taxi. Download the app (Bolt) and check how much it costs in advance.
From the airport
There are three options traveling from the airport to Oslo city centre.
First, there is the local train RE11 where you can buy tickets through the Ruter-app. The ride takes 36 minutes.
Second, there is the airport train (Flytoget) where you can buy tickets at the station in the arrivals-hall at the airport. It costs more, but only takes 30 minutes.
Third, there is the option to take the shuttle bus (Flybussen). Buy your ticket on the bus or using the app “Entur”.