Double click the background layer. (This will make it editable).
Re-name it if you like.
(I like to use the names of English explorers from the 18th century or different kinds of cheese. If you're a sporty type you could use the names of football teams for example. It really is up to you).
Do one of the following:
1. Delete the layer.
2. Click the little eye ikon to make it invisible (hide it).
3. Go to opacity and reduce as appropriate.
You do not 'need' to create a new layer but if you don't have a background layer to start with then this is an option.
Photoshop is like a box of chocolates really.
...but without the chocolates and a box.
What do you mean? What we've said is correct; how else do you have a transparent background if you don't remove the locked background layer via means of deleting or making it so that it is no longer visible (opacity as per Scotty's suggestion). I remove it all together, but that's just my personal preference... There are many ways to skin a cat in Photoshop, but it's best to keep things simple.