It all depends on how the existing switches are wired, so the first step is to map the existing circuit. Since it sounds like you haven’t done that before and probably don’t have the tools to do it, calling an electrician is not an unreasonable suggestion.
There are at least 8 different ways to wire a dumb 3 way, and that impacts how and where you add the smart relay, which is why all of this matters.
And you would have to be physically present to do the mapping to figure out which of the 8 ways applies to this particular switch and I don’t know if that’s convenient.
If you read the following FAQ, it has a discussion of these wiring issues. If after reading that you decide this is something you’d like to pursue yourself, we can discuss it further. And if nothing else, you’ll be in much better shape to discuss what you need with an electrician. 
The topic title is a clickable link. Note that the examples are specific to GE, so it’s not one to one for what you’ll be doing, but the concepts and discussion of existing dumb wiring should be helpful.