It is not as simple as that. First you need to know what fish you are after. Then you can match a lure to the fish. Then you have the task of working out how deep you want the lure to go...deep diving, shallow diving, surface lure, popper, twitcher, prop etc, etc. Then you have to pick a colour...
Here is a link to the Rapala site. Probably start with a saltwater lure, but there is no reason why a fresh water wont work.
I find Rapalas very difficult to cast. So they really don't work well for me when shore-fishing. You could try to add some weight to cast them a bit further. But that's basically what you have to do: cast out and reel in slowly with a few twitches here and there to imitate a wounded bait fish.
If it's the floating type and there is a strong tidal current running past the pier you could cast into the current and then let them float out with the current as far as possible and then reel in again. That also works quiet well in a river.
For me, they work best when trolled behind a kayak or boat. To get a better action in the lure, try to tie it on to your leader with a Rapala knot ( clinch knot ). Basically a little loop knot. It allows the lure to wiggle around more freely.
I honestly started hating rapalas! After trying out some really expensive and really cheap lures (over 150 in total), i have come to the conclusion that the best lures that work for me are actually in the mid price range (specifically i am hooked on Jatsui now and believe it or not BEARKING! which seem to be a better version of MOAB/DUO). These work great for me on Barracudas, landed me a 3kg one yesterday afternoon with a 18cm 29gr Jatsui (green).
But it honestly is not as simple as "what lure do i use to catch fish". There's FAR too much behind this!
What species of fish are you after? What time of year are you fishing? What range of colors are visible on the sea floor? (super important to most anglers) What time of day are you planning on fishing? What is the action of your rod? What is the casting distance you would normally cast (with full rod action)? What is the sea floor like? (rocky, sandy, combination? weedy?)