So what i think you want to know is how to send someone a flat (after they sent the tc)? Is that what you want to know? If it is, i know how, You want to start by sending them a message. When sending the message, type a thank you message for buying my texture ex. Thank you for buying my texture, Here is the flat. and now is how you send the flat.
On the message screen at the top there should be a picture of a mountain on it with a post card sign in the top right. Click that, then you register on like a website like photobucket(if you haven't already) and once you have done that, upload the flat on photobucket, Now you want to click on the flat and on the right should be a list of urls. Look for the one called "Direct Link", Click on it and when it says copied, you want to paste it in the box that comes up when you click the mountain looking button. Hope i helped! Thanks for reading, Hope i don't get ninja'd. o_o