Whats up dude, welcome to the site.
For a quick run down hit that edit button up there and check out how easy the code is.
If you indent, it will show up like this
If you want to embed a youtube video just do this:
You will see some code in the middle that is found at the end of the youtube video URL, and a number at the end which is the size you want it to be.
The editing page will help you with the rest.