To create a page, simply click the 'New Page" button.
When you are ready to share your creation with collaborators, click on the "Person+" icon and toggle the Share Link to "On".
You can now copy the share link and send it to whomever you like! They can view your page and if they want to comment or collaborate, they can quickly create a Free account.
From this share menu, you can also choose who has access to your shared page, and even turn the share link off (and/or reset it) if you no longer wish to share it.