Samsung themes

[Jiggy]

Hi, I'm new here and to the galaxy s8 plus, I've downloaded a theme from the Samsung theme store but after applying it the wallpaper doesn't fit the screen properly, it leaves a white bar on the side where the edge notifications etc would be, do I need to change a setting to make it fit properly? Any help will be welcome as it looks like a great theme just doesn't fit right

[Jiggy]

I have just downloaded another and it seems that after applying the theme the wallpaper is aligned slightly to the left (as you look at it) the picture is not centred although with this one there is no white bar, I assume it's to do with the size of the picture, very annoying and hopefully easy to fix