From the railway station, you can :
Walk to IRMA. It takes about 40 minutes. You can get a map of the city at the tourist office inside the railway station.
Take a taxi.
Take a tram line C direction "Neuhof - Rodolphe Reuss". The station is on the left when you leave the railway station. Stop at the station "Universités". Then go along the "rue Edmond Labbé" and "rue du Général Zimmer". The IRMA building stands on left-hand side (just after the bar "La Bohemia" located on the right side), at about 200 meters from the station.
From the airport you can :
take a taxi
take a train to Strasbourg. The station is situated on the right side when you go out the airport. You can buy a ticket in the station (4,30€).