New player, need a little help.

So im sure alot will laugh at me for this but whatever.

So I am new to the game, I have gotten some junk and stuff it says I can sell to a vendor. So when I go to the vendor, I right click as it states then it goes into the box where undo sell is to the right. I left click, I right click and it hops back into my inventory.

Ive checked the online manual and I cant find the proper way to do this so any help would be appreciated.

|||When it goes to the "Undo Sell" box is has been sold and coin has been added to your inventory.