User Roles

To assign a roles

Click on Users in left navigation

Select any user

At the top of the list, you can change the user role in the drop-down filter. (eg. Author)

Click Change

To assign or limit the capability of role

Click on Users > Roles

Edit any listed role.

Now, Grant or Deny the Capability that you want to assign (or unassign) to the role.

Click update button.