I've watched hours of tutoring videos all over the internet in search for an answer. This forum is probably my last shot at it. The gears on the left (for the front derailleur) don't change the gears on my bike, because the shifter cable is out. I've been trying to reinsert my shifter cable for my FD, but only gear one and two work, and it's too stiff for the third gear. Ahhhh! Please help!!
Sorry, there's no way to help with the info you've given. If you can post some pictures of the shifter, derailleur, etc. we may be able to spot something.
The basic things to look for are kinked cables or cable housing. Trying lubing up the cable, shifter, and derailleur, check the alignment of derailleur and the limit screws, and finally the cable tension.
There are too many possibilities, including the likely scenario of more than one problem. Find a qualified friend or a bike co-op, or Google "adjust front derailleur" and "install shift cable" Videos are great for seeing the process but not good at covering the details. Ignore the videos for now and look for results that point to sheldonbrown.com or parktool.com/blog.