Fiddle can go mid and support but he mostly jungles.
The jungle a lot of things but think of them as support for laners. They hold the lane when the laner leaves so that the tower is taken, they assist lanes with surprise attacks (ganks) which is something fiddle is really good at if you can use his ult in a place where you aren't seen. They also ward and help keep track of the enemy jungle. It's hard to do at early levels but it can make a big impact on the early game.
Teemo- your job is to annoy the hell out of who you're fighting. He's mostly taken top and rarely seen as support. You want to poke with your q and auto attacks and try not to take damage. You'll mostly face melee champions top lane so this won't be much of a problem.
Jax- good hyrbid damage top lane but requires you to learn how to trade and deal with match ups. Your jump will get you in close but you need your e to keep you safe from auto attacks and and stun the opponent. After the stun, get in one or two hits with you q (i think it's the q that powers up your next attack) then back off. Rinse and repeat. This is a simple trade, you hit them, they'll more than likely hit you back, but your goal is to do more damage to them then what they did to you. This is important for melee top laners and knowing your opponent's strengths and weaknesses are very important in this. Either google the match up or learn from experience.
Sivir- She has some of the best wave clear and pushing power in the game. By the time you get your second item finished you can destroy minion waves extremely quick. Be careful about pushing early on since it can leave you vulnerable to the enemy jungle. Your goal in lane is to poke the enemy ADC with your q and last hit as best as possible. If you don't last hit the minion you don't get the gold from it and you're gonna need that gold if you want to buy items. Also, her ult is one of the best engage tools in the game. As you play you'll understand on your own when your team wants go in and when it's a good idea to.
I'm an adc main so I wanted to add this: when playing ADC, watch you positioning. You want to be placed where you can attack the opponents without endangering yourself in team fights. Don't dive into the enemy team by yourself, that's not your job. Stay alive and do consistent damage.
