Holiness simply means something is "set apart." For a person to be "holy as God is holy" means they they need to a) repent and b) have faith in God's Word. Repenting is taking action, action means you're doing something.
People explain that the easiest way to define "repent" is the action of turning away, so in a Biblical sense you're turning away from sin and independance. But it's a two fold action... it's not just turning away from sin, but you're focus must be re-centered.
So in this case you're turning from sin/independance and turning to God/dependance. In doing this when your actions are God centered, they are moral and selfless and good in God's eyes. But we still have that choice to obey God or obey ourselves, thankfully God sent His Son to cover our sins and redeem us... that's where our faith comes in. To be holy means our actions are God-pleasing, but our actions aren't what saves us, our actions prove we are saved. Salvation come from grace alone.