You can only access it if you played and continued to play after they closed it off to F2P, or logged in during an opening period. Search Runescape classic on the homepage to find the World Select screen, or click here: http://www.runescape.com/classicapplet/playclassic.ws
If you wish, there's RSCEmulation which is a private server which is free to play and has more players than the actual thing. Chances are if you're asking how to access it, you won't be able to.
You can't play RuneScape classic if you didn't play it when it was out all those years ago, or if you haven't logged in RuneScape classic when Jagex released RuneScape classic for members for like 2 weeks.
- You need to have an RSC-account
- Search on the runescape homepage to Classic
- Load it, log in with ur rsc-account , password
- It does depend on what you like for sure! I personally love it.