For the initial application, you'll be asked to create a store so that you can get an idea of what Shopify actually is. This is a good chance to play around, and see if it is something that you actually want to work with, as you will be using the Shopify platform a hell of a lot if you get the job (as should be expected).
You can then expect an email from one of the recruiters, who will look to schedule a call. This call isn't a standard job interview, there aren't any stiff questions, it's more a free flowing conversation. Of course they are interested to hear a bit about your past, but you won't get much "What is your biggest weakness?" or other such cliches. It's more so that they can get a feel for what you are like as a person, as no one is expected to walk in and know this stuff. If you get the job, you'll see that the training is extensive, and so the interview process is more to see if you're someone that can fit into the team, personality wise, and if you have the mindset to grow and learn.
If that goes well, you'll be scheduled to do "the gauntlet" which sounds a lot more scary than it is. It's simply a 3 hour sample of what it's like to do the job. You'll have 1 hour of doing some test phone calls, 1 hour of test live chat and 1 hour of test emails. The questions they'll ask aren't particularly complicated, but you will not be expected to know them off the top of your head (although after a few months in the job, you will). This is more a test to see if you are resourceful, are you good with Google and other researching methods, are you polite, and do you have attention to detail when it comes to typing.
If you bossed the gauntlet, you'll then be schedule for another chat with one of the team leads. They'll let you know how you did and will get into the nitty gritty of the job. If you're happy with it all (which I guess at this point you are), then you're pretty much in. Congratulations!