1) Open the FLA file located in the folder SOURCES >> FLASH to edit the text.
2) Use timeline or flash library to locate texts, usually page symbol is named "pages"
3) Doubleclick it as soon as you locate the symbol. If the text is no clickable, then the text layer may be locked or you are in the wrong symbol (to find out if you are in the correct symbol, press "show/hide" button and if the text become hidden, then it is the one you need)
4) As soon as you can select the text and see regular text selection around it you can doubleclick the text and change it.
5) Usually pages and menu text are organized in one symbol, each frame is such a symbol contains a separate text. To edit such texts you should move to next frame and new text will appear on the same place
6) When editing buttons there can be some objects preventing editing or accessing texts, you should press "show/hide" button next to layer to hide the unnecessary objects.
7) After the texts is updated you should publish your FLA file to get SWF one. Go to File >> Publish or press CTRL+Enter for PC or Command+Enter for Mac to publish and you will get the SWF file in the same folder as FLA if you have default settings.