In general, you need to have a container with an arbitrary width. Before downloading the bootstrap, you can configure the grid, but I do not know how. Here you can set up http://bootstrap-3.ru/customize.php#container-sizes
3 answers
And I wouldn’t be in a hurry to set this width, it’s better to implement through offset, yes, you probably won’t get 100% of the desired width, but when the site doesn’t scale there will be no surprises, and if you specify a static size, they will be in love - as proof look at how the typography and other styles change when scaling, and yes, you can recompile the number of columns in the bootstrap itself, it will also help, but again, from my own experience, I’m not always a good idea on dynamic projects.
just do not specify the width to it - to erase existing values, it will be arbitrary
If the question of how to configure, then in the fields @container-tablet , @container-desktop and @container-large-desktop it is necessary to put down the value auto . Then the width of the container will not be a specific number, but usually depends on the type and content of the element.
But it is better to think about what sizes the container should have on each type of device and register them with this customizer, or install them directly in the style file during project development, although this is not so convenient.