To sell items to the shop as a bedrock client ( switch , playstation , pc ) you type /shop
Open the shop of your choice by clicking it.
Click on the item you wish to buy/sell
You will see a redstone torch below the item, please click that to toggle between buying and selling, once toggled to sell the redstone torch will be replaced by an emerald.
Click on the ammount to sell or on the emerald to sell all
