Hi baby09, I hope this reply isn't too late!
Since you want to change the setting only for all Picture Flash lessons in your courses, what you need to use is the Multiple Edit function. This will let you apply changes at one time for all the lessons you select, so you don't need to change them one by one.
Unfortunately, there will still be a manual step to this, which is selecting each Picture Flash lesson from the entire Semester. To do this:
> Open LR and go to Advanced Play/Edit, then select Courses
> Select the semester you want to work on
> Right-click on any folder then select "Expand/Collapse > Expand All" from the context menu
> Press and hold your CTRL key, then click on each Picture Flash lesson (you may choose to do this by batch, if selecting all of them is a bit difficult)
> Follow from Step 3 of this article: http://support.brillkids.com/entries/20586937-how-to-change-playback-settings-for-all-little-reader-lessons
** The particular setting you need to turn on is "Display words with pictures" in the Edit window's "Common" section
> As soon as you save the settings in your Edit window, these will get applied to all your selected Picture Flash lessons automatically