Conversations are full…or nor

So that is ok but how do I delete the old conversations so I can message people, because I am full, I can't message and I have played with it and can't find a way to delete the conversations. (just a few at a time) This is my first time back in a while and it looks like the geeks changed things around, and it is not as easy to navigate as before. Plus these pop up adds drive me crazy!!!
I gotta agree! But, I for one, have only Christmas gifted a gold membership, a d the site is a Huge help, not to Mention a Great Place, Full of Awesome People, so if they need a buck from The adds. Now, about that new layout! Lol