If you are interested in joining the group send an e-mail to Andreas Beyer with your CV and a motivation letter.
Andreas Beyer is a faculty member of the Cologne Graduate School of Ageing Research. You can apply through that program, but we also take students outside the PhD program.
If interested, you can directly contact Andreas Beyer. International researchers may also get scholarships through the prestigious DAAD and Humboldt Foundation programs. Please, check for eligibility constraints on their homepages.