Step1: Select the Tool menu at bottom. Then choose Text
Step2: Tap on 'T' at top menu to insert the word/message.
Step3: Align your text at this step.
Step4: Tap the configuration sign (top-right) to set other properties, ex. Color, Font, Shadow and Opacity.
Step5: Resize and move the text by dranging the bounding box. Any mistake, u can press the Undo button. Enjoy!