<link rel="stylesheet" media="screen, print" href="themes/smartadmin/css/formplugins/dropzone/dropzone.css">

. . .

<form action="http://<?=ROOT_APP_URL;?>/UploadToGallery" id="-gallery" class="dropzone needsclick upload" style="min-height: 7rem;" >
                                <div class="dz-message needsclick">
                                    <i class="fal fa-cloud-upload text-muted mb-3"></i> <br>
                                    <span class="text-uppercase">Drop files here or click to upload.</span>
                                    <br>
                                </div>
                            </form>