[Adding a stroke - thin border]

Thanks that works. Once I have added the stroke I want to change the canvas size with the background colour to be black.

I have unticked the transparent background  but can only get a white background. Is there a quick way to do this rather then having to put an layer behind and filling it with black?

[Adding a stroke - thin border]

I am new to Affinity but experienced in PS.

I want to add a thin border to an image. In PS I would select the whole image, go edit/stroke and it would give me the options 

of adding it inside the image, pixel width and colour. How do I do this in Affinity? Any help would be great.