Before importing your stereoscopic content in the editor, you need to add "_TB" (top-bottom) or "_BT" (bottom-top) or "_LR" (left-right) or "_RL" (right-left) at the end of every stereoscopic media name (images and videos) depending of how your stereoscopy is formatted. 

The editor cannot render stereoscopic content, you need to manage with raw stereoscopic content divided into two. This means we recommend to firstly import a monoscopic version of your video into the sequence editor, then to position your hotspots, images or text using the WYSIWYG to finally replace the source of the 360° media by the stereoscopic one. See animation below :