set forth on
set forth on somethingand launch forth on something
1. Lit. to start out on something, such as a journey. We intend to set forth on our journey very early in the morning. What time will you launch forth on your trip?
2. Fig. to begin presenting a speech or an explanation. As soon as John set forth on his speech, three people walked out. Every time he launches forth on a presentation, it's a half hour before he shuts up.