If you’re looking for an ausbildung here are a few addresses where you can find positions being advertised.
If on the other hand you have already identified a company you’d like to work with, you can call them directly and ask if they have positions and/or how to go about applying to work there. www.arbeitsagentur.de check under Jobbörse
Check IHKs in your area. Just google IHK “Name of town” or “Name of Closest City”
If you’re done with your Ausbildung and are instead looking for a job, you could check Finding a Job or Ausbildung in Germany.