Card Reader SDDR-83 V3 Image Mate 12 in 1

I have recently changed from using a Dell  laptop PC to using an iMac.  The cad reader worked well on the PC but I am unable to get it to download onto the Mac.  What steps are necessary for me to be able to get my new photos onto the Mac.  PLEASE use the simplest of computer terms since I am very unknowledgeable about computers.