This is what Potemy did to report someone..

"Click the drop down gear menu to the right of the 'Add friend' and 'Message' buttons.

Then click 'Report/Block...'.

On the pop-up, click 'Submit a Report' and under that, 'Report (name) account' and confirm.

On the next pop-up, mark 'This is a fake account', some more options will pop up, mark 'Gamer' and continue.

On the next pop-up, check 'Submit a Report' and continue and you're done."