I just downloaded mwo, now what?

The first thing a new pilot should do is hands down take a trip to the movement tutorial, get a feel for how movement works in this game. Unlike most shooters, MechWarrior operates with a torso that can twist independently of it's legs. This opens all manner of movement possibilities such as true strafing, circling opponents, twisting your torso to show stronger points and protect vulnerable/critical systems, and positioning yourself for shooting properly at different ranges of engagement. After you have finished the movement tutorial, you should refer to the post about mech roles and decide what role you would like to try first, grab the training mech that best fits that role, and go to the training grounds. (this is done by clicking on the gear picture to the left of 'launch' and selecting training grounds) group weapons using right control and arrow keys, then play around with the throttle decay and arm lock options. Press F4 to toggle 3rd person (from a competitive standpoint 3rd person is vastly inferior due to forced arm lock, loss of minimap, and the drone that you spawn gives away your position to observant players.) if possible feel free to go through this process with a senior member present to answer any other specific concerns raised while first learning.