I've posted 3 photos to DropBox.
You'll see in the photos that with the Pi3 there is no longer the "push insert/push eject" microSD card holder. Insertion is similar - just push until the card seats properly. To eject, you need to get a fingernail (or other thing item, like coin edge or screwdriver) to catch the raised edge about 15% of the way into the microSD card and then manually pull it out. Hopefully the photos help. Depending on how close the case is to the edge of the Pi, you might need to remove a 10mm (just less than width of SD card older opening) by 6mm (enough room to grab card) piece from rear of case at the edge/corner.
Please let me know if I can provide more info.