Regarding spelling, CKEditor has its own spell checker and also SCAYT. However, some bloggers may prefer to use the browser‘s embedded spell checker. For example, I use the «English & Greek» dictionary with Firefox, which really saves time as it checks spelling in two languages at once.
In order to be able to use the functionality of the embedded spell checker, you need two things: re-enable the embedded spell checker, which is disabled by default after CKEditor’s installation and then re-enable the browser’s original right-click context menu. That’s how you do it: