The local bitcoin looks good.
So I just sell my bitcoin to a seller or do I advertise my own bitcoin?
Whats the procedure or the easiest way?
Just sell it to someone already advertising. As you've just signed up and don't have any feedback nobody is likely to respond if you placed an advert.
Just click on the sell button next to the advert you choose and then fill in the amount and your bank details. Then you should get a confirmation that request has been accepted and then another when it is marked as paid. Check your online banking to see if it is there then release the escrow.