Trying to add files to my SD card via Nikon DX?

So my sister let me borrow her Nikon dx camera so I could use it as an sd card reader. I'm tryiing to copy a simple folder file (with.txt inside) To the root of the cartridge, but it just won't copy. I also tried the easy Right-click/Paste, but that doesn't work either.

A digital camera like your sister's Nikon isn't designed to be a memory card transfer device. It's meant to take photos and to use the usb cable to transfer images to your computer. Other files types aren't recognized by the digital camera.

You need to get a generic memory card reader (cheap at Walmart, Target, CVS, Walgreens, etc).

It doesn't work that way. You need another device to transfer to… A flash drive for example.