Used Late 2008 MacBook - erased HDD but can't download OS

Hi all,

Just brought a used late 08 MacBook (4gb ram, 250gb HDD) off of eBay, the lad who sold it left EVERYTHING logged in and all of his data still on it, I've logged him out of icloud etc (he sent me his password.........) but I wanted it reset so the OS and laptop would be linked to me. After erasing the HDD I have now found out that I can't recover OS over WIFI (it was running Yosemite) am I right in ordering snow leopard DVDs and how do I go about booting from the DVD?

Any help is greatly appreciated as I have no experience with MacBooks but wanted to try a used one before I go out and commit to a new one.

Cheers

DAn