Checklists are derived from templates. Therefore, in order to be able to create a checklist you will firstly need to have created a template.
To create a checklist click on the Quick Create button, which is the green button with the plus sign on the left toolbar. Then select the 'New Checklist' option.
A popup form will be displayed. Choose the template you would like to derive your checklist from and enter the name of your checklist. Then click the 'Create & Run New Checklist' button.
The checklist will be created and loaded for you.