Can I add checklists in Scrumwise?

Yes, you can add checklists in backlog items, tasks, sprints, releases, and projects. For example, to add a checklist in a backlog item, open the popup dialog for the backlog item, click the "More" link at the bottom of the dialog, and then click "Add a checklist":

Then add the checklist items by clicking "Add an item", in the checklist:

You can use checklists for many purposes, such as Definition of Done, acceptance criteria, requirements, to do lists, etc.