How do you save a selection in Elements 15 as a jpeg to then import into MS Publisher 2010?

I'm creating a birthday card in MS Publisher 2010. I already have a jpeg inserted on the front page for a background that I edited to 25% opacity in Elements 15. I want to cut out the figure of the birthday boy, using the magnetic lasso tool, when he was five years old (he will be 70) and then save the selection as a jpeg that I can then insert over the background image on the first page of the card. I tried creating a new blank file using the contents of the clipboard, where I had copied the selection and then saved it as a jpeg. When this occurred, the selection wasn't in the shape of the selection, it was rectangular, so when inserted into the card it was in a white rectangle.  I want no background so just his shape appears over the background photo. From my research I find that I will probably have to make the background of that selection transparent, which is beyond my capabilities, unless I can find some appropriate videos.

Is this the right approach, or is there another way to accomplish this? I wish I could merely edit-copy the selection to the clipboard and then edit-paste into Publisher, but I couldn't find a way to do this. The only way I can find is by using the insert photo command.

Thank you for your assistance.