Suprdav there is a barrel adjuster on the cable where it enters the shifter. You want to twist it out to tighten the cable, which pulls the front derailleur out. If you can get it adjusted with just that you're in good shape.

If you have to adjust it more than the barrel adjuster allows it's more of a pain because on the derailleur end there's no adjuster. Just a bolt holding the cable. You'd need to loosen the bolt and pull the cable slightly tighter, then fine tune it with the barrel adjuster.

To get it shifting right you may have to mess with how the derailleur is positioned on the bike. It's just a clamp around the seat tube. Unhook the cable first. Basically you want the derailleur arm aligned straight with the chain when you sight down it from the front. Position it up and down so that there's a dime's width between the chain on the big ring and the derailleur arm. Then hook the cable back on with enough tension that, with the shifter in second and the chain on the middle ring, it's not touching the chain on either side. Then mess with the cable some more to get it shifting both ways without ever rubbing. It takes some fiddling but once you get it set that's it except for the barrel adjuster now and again, which you can even fine-tune while riding if you want.