i dont know if there is an autoattack key, but if you just attack something, you will continue to do so until you command your champ to move or do something else.
Some key words to know that you might hear your teammates say in a game:
mia (bot, top, or mid) = missing in action. Means the enemy is not on the map, so beware that they might come for you.
b = hit 'b' on your keyboard to recall to your base to heal/shop
You should learn to type mia (area) too. If you are bottom and an enemy is off the map for a few moments, just type in mia bot so people know. Pinging the map also helps. I usually ping the crap out of a map if an enemy is gone missing. I think 'g' is to ping. I dont know, im at work and its just all natural when im playing. Pinging the map makes a ping sound
You will see there is a 'jungle' between lanes with some monsters
The golem with the blue swirly thing gives great mana regeneration and cooldown reduction (makes your abilities come faster)
The golem with the red swirly thing gives you a buff that slows the enemies when you attack them.
There is a dragon in the bottom right of the map by the river that gives some good gold
And there is a HUGE MONSTER (named Baron) in the top left of the map by the river that gives your whole team a big buff (makes em stronger) if you kill them.
Do not solo the Baron or the dragon (usually), you need your team
In the shop, under consumable items, there is a green item called a ward
It gives you vision of the map. To try it out, go the in the river and place a ward. You and your team will have vision of that area for the duration of the ward. It is VERY VERY helpful to know if you are going to get ganked (enemy comes from the side to kill you) and to just know where enemies are.
Try this for an Ashe build (this is the build people always get): Dorans Blade (attack damage), Berserkers greaves (movement), infinity edge (attack, critical strike), phantom dancer (i think in the attack speed section), then you can get a Banshee's Veil (defense, magic resist) or a Last Whisper (i think its in attack speed section).
That is the staple Ashe build.