Hi,
The issue comes from the fact that you've activated the "Use bootstrap v2 design" setting of HikaShop while your template doesn't use bootstrap v2, and thus, it is missing the CSS to place the checkbox properly.
A simple solution would be to turn off that setting. However, when you do, you might see changes elsewhere if you had already built around the bootstrap v2 design.
A safer approach would be to just add custom CSS to your website to move the checkbox to the left:
#modlgn-remember{ float: left; }