If you are looking for a PhD position at ITP, please contact first one of the professors/lecturers before applying for a position.
PhD position in GK
Information about applications for a PhD position in the Graduiertenkolleg can be found here.
PhD position in KSETA
The official application site can be found here.
Application for a postdoc position at the Institute for Theoretical Physics
The application site for a postdoc position at ITP can be found here.