Bad news for you, this option have been removed in chrome. Since the update of December 2015 the spell check option from the right-click menu disappeared and so you can not change the language for the spell checker as you normally would.
To add additional languages for spell checking, try the following:
- top-right 3 horizontal lines
icon ( ≡ ) > Settings > Show advanced settings > Language and input settings > click “Add” for Languages
- for each desired language, on the right-side tic the box for “Use this language for spell checking“. Then Chrome will show “downloading the spell checking dictionary”
Or you can just right-click in any text field and select Language settings. You will be there quicker 😉