Hi Allen,
You can either use "Ctrl+Shift+B" to set a bookmark at the current cursor position (in the sequence timeline), or
You can also right-click in the area above the clips on the timeline, but below the part that displays the time on the timeline (The area that says "Drag and drop your video, text and image clips here to overlay")
That will open a dialog allowing you to set the bookmark's name and bookmark color.