How did you set the container styling, and are you sure the syntax is correct? Can you find it using your browser developer functionality?
Whether or not there is any content present in your container shouldn’t affect visibility.
You will need to give the container a height and a width, maybe a bigger z-index too to bring it to the front. Then you can add the border, i.e:
These can all be added inline on the container itself, but it would be better to learn to apply them using classes in SASS.
You seem to be asking a lot of styling based questions – I’d recommend going through a free course on styling to at least get a high level understanding on styling stuff using css.