Enter the Zeeman building through the main gate, go left to the end of the corridor, through the doors, and up the staircase to the right.

Once in the first floor, go left into a corridor (next to the MRC office), following a "Toilets" sign.

At the end of that corridor there is a staircase, which you go up.

You are now facing office B2.26; go left, and find my office (B2.23) first door on the left.