Up in the corner of the message area where you read the messages, on the right side, it says BOOKMARK IT.
Click on that.
A little box will pop up. Most of us don't like this little box because you have to finaggle around it.
But here's what to do...
Once the box pops up, enlarge the box.
Then using the scroll on the side and bottom of the box, move it until you
can see where you hit BOOKMARK or whatever the words are.
Hope this helps.
If you don't understand this way, maybe someone else can explain better