Howdy welcome to the site!
first things first is to request access to the equipment exchange. You cannot list items for sale/trade etc outside of the exchange or your thread WILL be deleted
BEFORE YOU POST in the EE, you must read the EE rules thoroughly in order to ensure your ads are in the proper quantity and you are fully aware of any other restrictions and guidelines to save yourself trouble down the road.
third is to actually post your items for sale with a price.
some basic EE rules to get you started.
all for sale ads MUST have a price and you cannot have more than two for sale ads at a time in a specific EE area. You can list as many items as you want within those two ads though.
lastly make sure you post each ad in the appropriate section or they will be moved without warning.
to request access to the EE you go to your User CP then to Group Memberships where you can select to apply to the EE.
again, welcome to the site and look forward to seeing what you have to offer in the equipment exchange.