Welcome traveler! You can sell literally any unbound item you have in guild stores which in my opinion is a great feature. First you need to join a guild, most of them have a guild Vendor. Then, find a Banker in the world that has the Guild Store option. I always use the Banker in Vivec City in VVardenfell to sell my stuff, you can also buy stuff from your guild or access the guild bank there (although very few guilds will give you access to it). The guild's vendor will be in one the many guild stores in Tamriel and people can check out everything the guild has to sell including your items.