ATV 2 restore to 5.3

Please help just got a ATV 2 and I assume it has newest software since he says he restored it back to original settings. How can I restore to 5.3 ? I read I can manually through iTunes and downloaded 5.3 but have no idea what to do now. Any help would be greatly appreciated

if youre going to jb the unit, proceed with the jb process using seas0npass and youre good.

I tried several times and it says unable to save signatures so I assumed its because I’m not running 5.3. Thanks for quick reply!