How to display by using TLegend?

Dear ROOTers,
I want to display the box to distinguish the curves. So, I want to know how can I use TLegend. I have two curves, one for C and other for He (see attachment: CHe.root). Let above for C and lower for He and now I want to display it in box as an indication. If there is other tool then please suggest me.

Thanks in advance,

CHe.root (49.8 KB)

See the example here: