Since others have tackled the "where", let me jump in with some unsolicited advice as to "how":
Always ask questions if you have them, even if you might miss out of what seems like a good deal by taking the time to do so.
Allow me to build on my friend's recommendation a little... From your post-count...you are new here on the forums. WELCOME!
Often you will see a knife that has a few pics, but the seller may have listed little or nothing about the most imp parts of the knife: its intended use, grip thickness and length, the weight, spine thickness and blade length, type of grind, the blade-steel, and so forth. It makes it tough to buy a knife in such cases with so little information available in the ad.
I will usually turn to bladehq.com and paste in the name and model of the knife into the search box. BladeHq is only one of our excellent forum- supporting knife-shops, and this one usually list all parameters of the knife, including the SPINE thickness, which is of utmost importance to me...as it usually determines whet,her it's intended for light or heavy-duty use, and how well it will slice...
Also, many used knives on the Exchange is often nearly new, and you can save a ton of money(over retail) by buying these. And, if you do your research, you can resell a knife that you purchased, but don't like, without too great a loss.