Miz,
Welcome aboard!
No you can't edit or delete any postings. In any of the "section" windows (Front Page, Everything, Newbies, Hydro, etc) you'll see the newest four diary entries on the right hand side of the page about half way down.
Now that you've signed up you'll see a box titled "Menu" on the upper right side of the page. Many of us use the "Recent Activity" link to see everything that was posted anywhere including diaries since the last time we were here.
The "Everything" link at the top of the page shows all postings except for Newbies and the diaries.