Start by dragging & dropping elements from the Content list to the canvas.
Once you have the specific elements you need on a certain page, click on it on the canvas to open the editing options in the panel on the right.
For each content item you can:
Edit the Content
Edit text
Upload images
Add / delete answers
Define answer text
Reposition answers
Set correct answers
Add video URL
Change the Design
Edit font options
Edit content background color
Edit highlight color
Set alignment
Edit border
Define additional Settings
Edit link to URL / project page
Edit display option
Define answers click behavior
Edit answer alignment
Define text area type
Edit video options
Move or copy an element among pages
Once you've selected an item on the editor canvas you can press "cmd / ctrl + c" to copy and "cmd / ctrl + x" to cut that item. By pressing "cmd / ctrl + v" you can paste that item.
You can do this either on the same page or on any of the other ones within the same project. All the design settings and functionality will be copied along.