You'd have to "Promote" your item from the Side Shop, or so I'd imagine, to get it into the newspaper on the News Stand. I don't think you'll be able to see your own items, though. As for how to sell crops, when you select a slot on the Side Shop and the menu pops up, click on the Silo tab on the right. It is below the Barn tab. This lets you switch between Barn and Silo for your items to sell.