You have to buy Leopard on disc. Apple no longer sells it and is not available to download from any legitimate source.
... i have downloaded it from the apple website and it tells me i need os x 10.5 to run the software
You downloaded an update, not the operating system. As the installer dialog indicated, a previously installed Mac OS X 10.5 must be present to update it to 10.5.8.
Check Amazon or other software vendor.
Hello and Welcome to the Support Community
Mac OS X 10.5.8 is an update to Mac OS X 10.5. Treat this like a service pack like SP3 for Windows.
You can't apply a service pack to Windows, without Windows being installed.
You may Have Mac OS X 10.4 installed currently. In order for you to run 10.5.8 you need to install Mac OS x 10.5.
This can't be downloaded for free, you have to by it on DVD and install it.
It's called Mac OS X 10.5 leopard.
You can buy it from venders like Amazon or eBay. It's not cheap to buy
Hello, I just got a ibook g4 as my entry into the world of apple ...
Realistically, an iBook G4 hardly qualifies as such. It is ages old, a lifetime ago in computer terms. You will not be able to accomplish half of what most people have expected of their computers since then.