From inside your folder, you can select "Add some" or the button "Add Lessons".
Once you select any of these options, you'll see a pop-up window with a list of all your lessons. Select the ones you'd like to add and hit "Add".
And voila! You'll find the lessons inside the folder!
You can also add lessons to folders within your the main area of the library. To do so, click the more option and then select Add to > Folder
For steps on how to create a folder please visit us here.