To modify a sequence:
1. Go to the Sequences page (1)
2. Select the sequence you want to modify clicking on it (2)
3. Once you are in the sequence, you can update :
the content of your steps (emails , tasks, calls,...) using the My sequence tab (3)
the settings of your sequence using the Parameters tab (4)
the content of emails for specific contacts of your choice once your sequence would be launched using the Emails tab (5)
the title of your sequence using the little pen (6) at the right of the actual name of the sequence
the time slots for your steps and the delay between sequence steps, using the blue bricks (7)
4. Once you updated your sequence, make sure to hit the Save the sequence button (8)
Here are some articles to help you modify and configure your sequences: