You can't link your RS account to your OSBot account... Even if you could, why would you? That's like telling jagex you bot and asking for a ban.
If you're trying to get an old RS account back, you need to go to runescape.com and go to forgot password and see if you can get it that way. If you had a registered e Mail on the account, I believe you should be able to get the user for the RS account.