The route is very obvious: You walk up where it appears flat and easiest. There is no fix route and there will never be a track, especially in the upper parts: There you have to find out yourself, how to circumvent the crevasses. Once you reach the crater rim, a short passage to the left will carry you to Haakon VII toppen, the highest spot.
This only applies in excellent weather. The slightest question mark in that respect means you have to postpone any activity. Until your time on the island runs out ...
"As an adolescent I aspired to lasting fame, I craved factual certainty, and I thirsted for a meaningful vision of human life - so I became a scientist. This is like becoming an archbishop so you can meet girls."