Add .form-inline to your form (which doesn't have to be a <form>) for left-aligned and inline-block controls. This only applies to forms within viewports that are at least 768px wide.
May require custom widths
Inputs and selects have width: 100%; applied by default in Bootstrap. Within inline forms, we reset that to width: auto; so multiple controls can reside on the same line. Depending on your layout, additional custom widths may be required.
Always add labels
Screen readers will have trouble with your forms if you don't include a label for every input. For these inline forms, you can hide the labels using the .sr-only class. There are further alternative methods of providing a label for assistive technologies, such as the aria-label, aria-labelledby or title attribute. If none of these is present, screen readers may resort to using the placeholder attribute, if present, but note that use of placeholder as a replacement for other labelling methods is not advised.