How to assign permissions for staff users
Hover over the staff account in question, then click the "edit" button to open that user's settings.
Next, navigate to the "Permissions" tab.
The most commonly assigned permissions are already configured. You can dig in and tweak them to your heart's content. Simply start in the area that you're looking for, and drill down until you find the permissions setting that will meet your needs. Additional options will be added in the near future.
As seen here, you can toggle access to entire modules on and off:
Or you can drill down much deeper. For example, by clicking the "SEO" option, you can choose whether to toggle it's sub-modules on or off for this user:
And you can drill even deeper than that. For example, by drilling down through SEO --> Rankings, you can choose whether to allow this use the ability to manage keywords:
When finished setting permissions, click the "Save" button to save and exit.