How do you contact the seller?

im on console and i wanna buy an item which the seller is selling and their willing to negotiate the price. Thank you

@Hollow-Ichigo00 What i like to do to save time is buy the cheapest item they have and write my price in the kudos section. Hoever if you want to contact them, in game you have to get their PID and send them mail/whisper/etc to contact them. To do it by gamertag they will have to have it on their little menu info if they do want to be reached that way.