Start by creating a new post on the create page, using the editor to create a brand new web page. Choose your options, press submit and you'll be taken to your newly created page. After that you can copy post url and can share it online, with your friends or on social media!
Once the post is expired, then the contents of the post will be deleted forever.
On post create page you can check on checkbox 'password protected' which would show the password input option with pregenerated password text or you can change it as well if you want. And after the post is created with password it won't be accessible without the given password.