You can start new lifecycle workflows or manage active lifecycle workflows for an account through this page.
To deploy a workflow to an account, click "Start Workflows". On the pop up modal, find the workflow you'd like to use for this account and click "Deploy".
To manage workflow tasks for this account, click "Details" for a workflow, a filtered view of all the tasks associated with this workflow for this account will be shown in the main task page. Click on each workflow/milestone task to check off the items that have been completed for this account, add additional subtasks and provide comments if necessary.
Read more about managing workflow tasks.