To get to the Embassy you can take the Nº 19 tram. There is a stop at "Meltzersgate" Street.
From other places, you may take the subway (any line) and get off at "Nationaltheatret",
Walk along "Drammensveien" (it is an approx. 20-minute walk) towards the Castle until you get to Inkognitogate. Turn right and go on until "Meltzersgate" (see map).
If you are coming from another city and arriving to the train station Oslo S, take the train at "Jernbanetorget" station and get off two stations away at "Nationaltheatret". You may also walk along Karl Johan Street towards the Castle following the aforementioned way (approx. 20-25 minute-walk)