The is an answer in FAQ:
“…use the bookmark button at the top of the lesson page beside the print icon. When you click on the button you will see additional bookmark icons beside each paragraph. Drag the bookmark from the paragraph you want to mark into the bookmarks toolbar. The next time you want to return to that lesson and that location click on the bookmark in your toolbar.”\
But I do not see bookmark button, do not see bookmarks toolbar when i am learning some lesson!
Please, help me to get it!