The purpose of auto-propagation is to leverage repetitive segments and re-use content. Configure and enable your auto-propagation preferences under Preferences > General Preferences > Auto-Propagation.
To leverage repetitive content:
Select a segment for translation in the TXLF Editor. In this example, a filtered search locates and identifies duplicate segments.
Enter the translation for the first target segment.
Click Next Segment or press Alt+Down to update the TM, move down one segment, and leverage the next segment from the TM.
Once you commit the target segment, this action automatically propagates the TM updates to target segments throughout the file, based on segment preferences.