You don't need Steam, Spring is independent from it.
Just a note in case you want to get some practice before the game: the BA community is pretty forgiving towards new players, as soon as they know how to set up a decent start (Metal extractors (Mex) - Solar Power plant (2 or 3) - Kbot/vehicle lab and then a radar and AA. Preferably also a turret). If you start mucking about (building a wind farm without even getting a lab, building an air base while you're at the front lines, blocking others from building mexes with mines or something) they'll get pissed. Also, you can assume that everyone rushes because mexes have piss poor health, so be prepared for that (or do it yourself). Rocket units are always good even up into the late game, so I suggest you focus on them unless you absolutely need to fire over the rubble piling up, in which case you get the plasma Kbots. If you go vehicles, Levelers (for Core) or Janusses (for Arm) are excellent for taking out large groups of weaker units and the Janus can blow up a light laser tower with a single volley.
One last thing to remember is to ALWAYS reclaim all the metal left over after a battle if you can. You're usually short in metal (unless you're building a geothermal power plant, in which case you get a chance to store some metal), so anything is useful. Don't be afraid to use your commander for that but be sure to make sure you can retreat in time (especially Janusses deal huge amounts of damage to a commander) Blowing up a commander gives you a corpse worth a whopping 2500 metal and a huge explosion to boot, so do that too
If you start on water, which is rarer, use the same method but build a scout boat and directly follow up with a cruiser or corsair or whatever their name may be. The other ships are more powerful (though subs can't attack land targets), but they take longer to make, meaning the opponent could take down the lab before they finish. T2 ships have huge range, so using them as mobile artillery to clear a bridgehead or just to level seaside bases is an excellent idea, especially if your team has control of the sea. If you don't, it's better to stick to T1 ships for a while and try to gain the upper hand before moving on.
Also, while sharing commanders is an option, you can also have teams with multiple independent players and an equal amount of commanders. This means people can start on different locations and you'll have to deal with multiple cores. BA is not a game where you stick to your base though, so expect to find resistance across the whole map