Before you can use 
Live Spell Check, you need to download and install spell check dictionaries for one or more languages. You can easily do so right within AceText. On the Appearance tab in the Preferences, click the button “Download Spell Checker Dictionaries”. AceText will then connect to the Internet to fetch a list of available languages.
If you want, you can choose the folder into which the dictionaries should be installed. If you specify a folder that does not exist, AceText will create it. All dictionaries must be installed into the same folder. If you already installed some dictionaries, and then install another dictionary into a different folder, AceText will move the previously installed dictionaries to the new folder.
To install a dictionary, click on the language you want in the list, and click the Install button. AceText will then automatically download the dictionary, and install it into the folder you specified. A progress meter will appear while downloading.
You can have as many dictionaries installed as you want. There is no need to uninstall dictionaries. However, if you want, you can select a language and click the Uninstall button to delete a spell check dictionary.
If you are behind a proxy server, and AceText is unable to detect your proxy settings, you can change them by clicking the Settings button.
Due to firewall and other network settings, it is possible that AceText cannot connect to the Internet directly. In that case, you can manually download and install the dictionaries from https://www.acetext.com/spell.html.