Embrilliance Essentials is a sewing and embroidery design software - compatible with both Mac and PC - that will give you a lot of flexibility if you are trying to merge applique or embroidery designs.
I use it with my Brother SE2000 and Brother SE600 embroidery and sewing machines.
There's a free version of Embrilliance, but if you want a lot more features you'll want to do the one time paid upgrade to Embrilliance Essentials. In this tutorial I'll show you how to download Embrilliance Essentials for beginners on a Mac. The process is essential the same on PC.