Hi, thank you for contacting JustAnswer.com. My name is Russell. I will do my best to provide the right answer to your question.
First of all, you can get those designs onto your Viking machine, and you should be able to work with them too. It does not require a PC.
Here's a site to look at, with regard to that:
But that, and its download section, may not answer your question.
Your answer is: first you need software to work with and load the designs on your Mac.
(If you already have that, skip to the next step:)
Then you connect your Viking machine to the Mac with a USB cable. ]
And if you have the right driver for the Viking machine, or if you are just plain lucky and your version of MAC OS X on the iMac has such a driver for your Viking machine, then it will just work.
If it hasn't already just worked, please tell me the MAC OS X version on your iMac, and I will advise you further.