A quick and dirty 'How to play'.

If you're new to the Total Annihilation, Supreme Commander, Planetary Annihilation style of RTS, here is a very basic overview of how to play.

Resources:
There are two resources. Metal and Energy. You need to build metal extractors on deposits. You can build Energy generators anywhere.
The numbers at the top middle show you your current stash of each resource and the green/red number shows you how fast you are losing or gaining it. It's a shared pool. All fabrication units draw from it, so when you have a lot of fabricators making stuff you'll probably get some big red numbers and all of your construction will start to slow down a lot (because the resources you are generating cannot keep up with demand, so the trickle that is coming in gets split over all your fabrication units).

Tech levels:
To get access to higher level units you will need to have one of your fabrication vehicles build an advanced unit factory. That adv. factory will be able to build better units and also an advanced fabrication vehicle which can build even higher tech stuff. Your commander can only build the basics structures.

Queuing buildings:
When you are telling your fabrication units to build buildings you can hold shift to set up a build queue. Grab one fabrication vehicle and tell him to build a big circle of missile turrets around your base and leave him to it.

Orders:
Setting units to patrol is really handy. Grab a bunch of units, click the patrol button, hold shift, and click a bunch of way-points. Fabrication units on patrol will repair buildings (and units?) that are damaged.
Selecting a group of units and right clicking another unit will effectively make them guard that unit. They will follow it and protect it and fabrication units will repair it.
You can give orders to a unit factory and units built there will follow the order once they are completed. It's a good way to have a constant patrol of scout aircraft circling outside your base (give the air factory a multi-point patrol order).

Radar:
Radar is super important. Get it up (hu hu hu), get it everywhere, and you wont get surprised by a big wave of enemies coming in. You've probably never played a game in which radar coverage was so important.

Basic advice:
Always keep improving your resource generation. Don't forget to upgrade to advanced metal extractors.
Always keep radar coverage up and have more than you need. You don't want a quick assault blinding you for 10 minutes, because the big wave of baddies is probably following.
Scout lots. Send those little fast guys all over the place and don't stop doing it.
Don't move to advanced tech too fast. It's really draining on a newbie economy and that's slow your building speed to a crawl and get you way behind.