You need about 15 minutes from the station (if you don't get lost). One possiblity is walking.
Another possibility is to take a tram (underground) U11, U17 or U18 from the train station and get off after two stops at Berliner Platz.
You then have to walk about 200 meters, so that the big shopping centre Limbecker Platz is facing your back, and IKEA remains on your right, on the other side of the street.
The department is in the same building as Conrad Electronics used to be. The ground floor is empty at the moment.
Our group is on the third floor on the east side of the building. If you don't have a compass look for the letter O in the numbering of the offices. (O stands for Ost = East).