[Circling an object in a photo]

I can't figure out how to draw a circle/oval around an object in a larger photo to draw attention to that object. I simply want to be able to draw a white/black/yellow line around an object without obscuring the object itself. Since there's no manual to speak of, and I've spent quite a bit of time exploring Affinity, without success, I'm hoping someone can provide specific instructions on how to do what should be a simple task

[OS version?]

Just purchased Affinity Photo on the basis of online reviews, your own web page, and an Affinity response to an earlier question about its compatibility with OS 10.11.6. Opening splash screen wants me to upgrade my OS to 10.12, which will render useless much other software that I use regularly (that's why I asked about OS compatibility in the first place). Before I spend another minute on it, will this program run on OS 10.11.6?