From the Sequences menu, click on: (Sequence) > Emails. Hover over the active email for the Prospect and a drop down arrow will appear on the right. Click the arrow and choose 'Edit'.
If the user chooses to delete an email in a sequence, the user would choose 'Delete'. Deleting an email in the 'Emails' tab will cause the Prospect to be paused in the sequence. To get the Prospect moving through a sequence again, the Prospect needs to be resumed. See Resuming Prospects In A Sequence.