Click ctrl + shift + P and look for Dione: Save Credentials. Make sure you have your Confluence Token ready. Use the email you use when logging in to Atlassian. This is a one time step, you don't have to do it if you used the extension before.
Click ctrl + shift + P and look for Dione: Login. This will take to an external website, where you will get remote access to your Confluence workspace through Dione.
Click ctrl + shift + P and find Dione: List Pages. Choose the page you wish to see in your editor. The page is converted to Markdown by default.
In anoter tab, select the code snippet you want to document. Click right button on your mouse and choose Dione: Codify from the menu. You can do it multiple times.
When you're happy with your changes, click ctrl + shift + P again and choose Dione: Push Pages. You should be able to see the changes in your Confluence.