Well, if you wanna' play before this weekend, just too learn a bit, here's some tips just off the top of my head.
Try and play Player Vs. CPU games on Classic in Beginner mode. You might want to tell everyone to go easy on you, because you are "Teh Noob"
There's a little goblin dood that sells items near the spawn point (or you can click on the icon that looks like it'd be a shop at the bottom). At this point, you should just buy the stuff at the top that says recommended in the order it is listed. Also, the first one is mostly just a throw away item that is only useful for early game, so once you feel confident you don't need those boosts, sell it to get some gold for something better. Also, items can be "upgraded" from other items, so if you see a little tree thing, buy the cheaper stuff when you only have that much gold. You'll end up paying the same amount of gold whether you buy the bigger item or the individual items.
In Summor's Rift, people usually divide up with 2 people on the outer lane and one person in the middle. Someone might instead go out into the area in between, and hunt the monsters that live out there, but there will usually be at least one person in each lane, and the bots will always go 2-1-2. At this point, just see where everyone else is going, and go where there is the extra spot.
Anyway, your main goal early on is to push back the waves of minions so that you can kill the enemy towers. This tower will destroy you if you let them hit you, so always have a swarm of your own minions around you. Also, if you attack an enemy champion while in tower range (enemy champ can be anywhere), that tower will start attacking you. So, don't go attacking enemy champions while near a tower unless you know for sure you'll get the kill.
Another important skill that you should try to learn is Last Hitting. You get experience when enemy minions die near you, but you only get gold if you strike the killing blow. So, try to make sure either you or your partner in the lane are getting that last hit on the minions.
Also, never run into the enemy spawn point. Your face will melt like in Raiders.
p.s. Spin to win
I am not a reasonable man.