EasyOffice includes predefined spelling dictionaries in a variety of languages. When you add a unique word to the dictionary, the word is not actually added to the predefined spelling dictionary that you are using. It is added to your user dictionary.
Put your cursor on the word. There is no need to select the text.
Go to the Tool menu, and click Add word to dictionary. (Or, right-click to access the Quick-task Menu, and click Add word to dictionary.)
The word will automatically be added to your user dictionary.