You style a form pretty much the same way you style anything else. Typically, you assign the appropriate css classes to the form elements, with those css classes defined in a .css file.
How this is done depends upon how you’re rendering your form fields. If you’re rendering the fields manually, you can specify classes in the attrs argument to the widget. If you’re using a Crispy layout, you specify the css_class on the element.
For us to provide more specific details, we’d need to see the form and how you’re rendering it. (For example, specifying attributes for a widget in a ModelForm is slightly different than how you would do it on a regular form.)
I’m using bootstrap and the style seems fine to me, the problem is that I don’t know how to put, for example, two fields in the same row, or three… mostly structure it as I want but following the style it has.