Hoo boy, where do I start? I suck at explaining/giving advice xD
There's quite a bit to learn. ADCs must always watch their positioning at all times and keep an eye on the map. Just know that ADC's primary concern is farming minions. Minions are easy, reliable sources of gold, kills are not. Some matchups are worse than others. Just know that if you play a short-ranged ADC, you will be at a disadvantage. Longer range ADCs can poke/harass w/o much return dmg if they play well. I'd probably recommend Caitlyn or Ezreal as they are pretty safe carries with their range + mobility (though, its very easy to shove ezreal under the turret so you'll have to learn how to farm under tower. 2 tower shots + 1 AA for melee; 1 AA + 1 Tower + 2nd AA for casters). Another thing to note, as I assume you know as a support player, stay parallel with your support. Side by side. If the enemy botlane (or jg gank) focus your support, don't just run away, attack as you are running. They aren't focusing you so you are free to damage & possibly turn the fight/get a kill.
Don't mindlessly attack the minion wave, especially if you dont know where the enemy jungler is at unless you are sure your duo has the better matchup. When the enemy adc walks up to last hit, fire an AA at them (They'll have to make a decision whether to take dmg for the CS or to trade back, missing the CS). When you are pushed up to their turret, you can either try to poke them while they're trying to farm under tower, or get free shots on the turret (be careful of positioning!). If you ever get alone time with the turret, try to use your autos on the turret rather than the minions, except for last hitting. You can kill minions with spells, but you can't dmg turret with spells, only autos! But it's also good to clear the incoming enemy wave so that your minions can stay alive to attack the tower (and for the minion backdoor bonus).
As an ADC you have to attack the closest target in range that is the highest priority. Mainly tanks but if you can safely attack another champion, attack the highest threat. DO NOT TUNNEL! It's ok to only get 1 or 2 attacks off and then change targets. Look up Stutter Step/Orb Walking & Kiting. Just always try to stay at your max AA range (thats your advantage as a ranged/ADC champ). Atk, move back, atk, move back (or forward if you are chasing). Moving targets are harder to hit. Never just stand still.
Wow, didn't realize 3 paragraphs already. I'll stop for now lol. Hope this helps!
