In Central Station, head to platform 7. Take note that 1st and last coach is a quiet coach, meaning you should minimize the tone of your voice, phone on mute and be mindful of your movement/noise. Better stay in the middle coach. It will be around 2 hours, so don't miss Katoomba stop, otherwise you'll reach Mount Victoria.
Scenic World
From the internet not much says about the quickest access to Scenic World - mostly website suggests to take the Blue Mountains HOHO and the Troley Tours. Please be aware that there is Bus #686 run by the government which accepts Opal Card.