Upgrade New Install 2.6.5 to 2.8.4

I created a new install on our hosting acct with Fantastico ..but it was version 2.6.5..and I need to use plugins that support 2.7 and above. Before doing anything to the blog …no set-up no plugins…I decided to upgrade immediately to 2.8.4 I can not find step by step upgrade instructions. I downloaded the 2.8.4 file …already. Can you send a link to the upgrade instructions. I’m a rookie but can use FTP on our hosting account. THANKS VERY MUCH
Paul