Before trying to delete an entry make sure that you have page edit permissions.
There's an entry you want to delete? Just like with editing entries there are two ways to do it.
Using the in place delete button
The Diary has a feature which allows you to easily delete your entries while viewing the page. Simply hover over the entry you want to delete and click on the trash can.
You will be asked if you really want to delete your entry. After clicking "ok" the page will be reloaded and your entry will be gone.
Deleting entries using the page editor
Just like with editing entries you can of course also delete them by using the page editor.
The easiest way to do this is by clicking into the row that you want to delete and then removing it by clicking this button:
Wow, just like with editing entries the in place deleting mechanism can be pretty useful, right?
Now that you're almost an expert in using the Diary you should read about Anchorlinks.
Note that since everybody who has page edit permissions can edit the entry table, and therefore delete your entries, they can also delete your entries using the in place deleting mechanism.
Note that if you delete an entry via the in place deleting mechanism there will be a message about it on the updates stream of your Confluence. This also includes a short preview of what you have deleted.