You've got that backwards. Your mod is the iStick40W and your tank is the Magnanus.
The coil is in the bottom of the tank. In this pic, the "coil" is second from the right.
Watch this video to learn how to prime the coil and replace the coil. First part of the video is a review of e-liquid, so skip ahead for the tank part.
Your 40 watt mod might be a little underpowered to fire the coil of that tank (20 - 150 watts)