Hi Albert! having been here as a regular for over 6 years and a brief experiment as a seller, literally all you need to do is click on the "0 for sale" tab at the top of the page and list what you've got to sell with some good pictures and descriptions!

if you take a look around you'll see a few vendors who despite being some of the most openly disgraceful, unbearable, cocky, offensively stupid, intentionally antagonistic and outwardly offensive people on the entirety of the internet they still reap immense success on here

unfortunately this unearned success goes right to their heads and despite them being frequently publicly disgraced, they can still make a killing on here because all you need to make sales is items on the item wall

though now that competition has become a lot fiercer, nefarious tactics often get used to keep a listing / item at the top of the wall or closer to the top, which of course will help with sales by a pretty significant amount which is why the competition for that top spot is so fierce

so if you can't get much visibility on the items wall, post a random topic a few times a week and people will be much more likely to see you, this is why a lot of vendors post topics daily now!