I use one. The extension tubes will dictate the magnification. All you have to do is place the glass at the native focal point of your scope. Then add up tubes at the back. Top of my head I get x3 mag minimum with x5 if I add let's say 180mm worth of tubes. There's a PDF on the astro-physics site with all the distances. As you add tubes the focus slightly goes inwards but it's within the ball park of native focus. I use the GSO 2" tubes.
