Use this phrase to talk about accomplishing some kind of goal. You explain what the most important or last step toward that goal is with the phrase "it's just a matter of ___":

You'll get the hang of it soon. It's just a matter of relaxing your shoulders and swinging the club smoothly all the way through.

We've gotten permission from the city council to do it. Now it's just a matter of finding the funds to make it happen.

You can also use a noun after "it's just a matter of":

Anyone can do it. It's just a matter of practice.

In the example at top, the woman's goal is to get all of her stuff settled in her new apartment. Unpacking the boxes is the next big step toward her goal. That's why she thinks "It's just a matter of getting everything unpacked."