Currently Being ModeratedJun 29, 2013 9:33 AM (in response to zaque2004)
Select all the items you want to check. In this case it's all your songs, so go to the Songs view and press Command + a on your keyboard to highlight all the songs. Then, right click anywhere and select "Check selection."
Currently Being ModeratedJun 29, 2013 10:57 AM (in response to neil95)
Thanks, Mr Neil95. Solved the problem. I had to use Control as my Mac Mouse doesn't right click.
I had done similar earlier, but tried to use the checkmark at the top of the column. That gave me a different dropdown menu. It did not have "check selection".