Hint: To show spelling errors in a separate pane you have to install a dictionary.
From the ribbon click on the Show Pane menu and turn on Spelling Errors
When a chosen spelling dictionary is installed, your spelling errors for the currently open segment will be displayed in a separate pane, above the Translation Memory pane.
When you right click on a spelling error in the pane, you can choose to ignore the error once or ignore in all instances.
Related Article: How to add a spelling dictionary to the translation editor