To open Workflow Scheduler for SharePoint Online (Office 365) navigate to Site Contents and open Workflow Scheduler app:
To open Workflow Scheduler for SharePoint 2013 navigate to Site settings:
Then click on Plumsail Workflow Scheduler in the Site Administration section:
You will see the list of scheduling tasks. To add new task click Add new task:
Then fill the task name, choose the workflow from the list of workflows and specify schedule:
For advanced scenarios you can use advanced type of schedule. To understand how to work with advanced schedule read how to create advanced schedule using cron syntax.