Use spell check across your entire script or while editing text in each element on a layout
To turn off spell checking as you type, choose Edit->Spelling->"Check Spelling as You Type" to deselect it (make sure the checkmark is not visible next to the command).
To check spelling from the insertion point to the end of the script, click to place the insertion point and choose Edit->Spelling->Check Spelling.
The first misspelled word found is highlighted. You can correct it or choose the same command again to continue checking the script.
The Spelling window opens and you can use it as Working with Spelling Suggestions describes.