couldn't add docklets to plank

i want the add gnote screenshot file uget on plank but couldn't find a way. i added those icons to desktop then draged them to plank it worked but thhe problemm arises here i dont want them to be on my desktop just wanted them on plank so i put those icon in trash as i couldnt finnd a way to get them off my desktop but after that those icon disappered from plank also and plank doesnt accept drag n drop from menu.
it would be great if someone can guide me.
thanks a lot in advance