How does trading on here usually work?

I've been passively collecting coins for 14 years and more actively collecting for the last four or so, but I've never done much to organize and never cataloged my collection. I just started the big task of sorting through my various jars and buckets to put them into binders and pull out duplicates. I'm using this website for that. I like the idea of trading with other collectors over just buying my missing coins and I'm just curious how that usually, generally works.

Thank you for your time.

On top right of this page is the FAQ section which will help.
https://en.numista.com/help/index.php

I have had a couple of excellent trades whilst on numista, I highly recommend you to look at what is on offer in the swaps section.