Step 1: Click the “Send” step.          

Step 2: Click the checkboxes next to the contacts you wish to edit. To quickly select all displayed contacts, use the checkbox in the very top left of the mailing list grid. You will know which contacts are selected, because the row will change to a light green.

Step 3: Click the "Edit" link

Step 4: On the Bulk Editor popup, choose between editing tags, removing data, editing the RSVP Due Date or updating the Plus 1 Allowance for the selected guests.