Hey, this is how selling works here at EpicNPC.
You visit the forum section where you want to sell your account, since you want to sell your WoW account you should visit this section of EpicNPC:
http://www.epicnpc.com/forums/92-WoW-Accounts-Buy-Sell-Trading
And go to the right category for your account. Now you are gonna start a new thread where you want to sell your account, the button to create a new thread looks like this:
Once you open your new thread you put in a title, remember that you need to have pictures in your thread or it is not accepted, this is an example of what your thread could look like:
When you are done with making your post you need to submit it, you do that by clicking here:
Now when you put up your post you need to wait for someone who wants to buy your account, they will either send you a PM here on EpicNPC and you can talk to them there or they might want you to add them on skype, however remember don't go first unless you feel like you can trust the person you are trading with, i strongly suggest you to use a Middleman provided by EpicNPC.
Also for the payment, you two have to come to an agreement when it comes to payment because EpicNPC does not have any responsebility for your payment agreement, i strongly recommend you two to contact a middleman that is trusted so you can have a happy and fair trade, happy selling/trading!