Click the misspelled word with the mouse and it changes to a textarea that you can edit. This has to be available through the keyboard as well. Related to http://feedback.telerik.com/Project/108/Feedback/Details/126937-add-tabindex-attributes-to-the-radspell-dialog-elements
A possible workaround is attached. The DialogScriptFile is used to add tabIndexes and override some internal methods in order to provide a keyboard event. In the sample the misspelled word TabIndex is hardcoded to 2 and you need to leave room for it, regardless of the position you choose. It cannot be dynamic.