You need to be much, much more specific. There's a million ways to animate characters and the prerequisites range from what kind of graphics it's based on to specific shot composition. No point in generic and broad "Can I...?" questions. Yes, AE can, but the details will differ from situation to situation. Everything else would be a bottomless barrel of advise that won't help you in any way. And, no offense, since it seems you're not even aware of waht AE is capable of and how it works start by reading the online help and/ or look up a few tutorials on the web to even get an idea what you're facing.
The techniques range from 2D MoCap using character animation to live footage used as a reference for traditional animation. You can go from here:
It depends on what you want to do and how much time you have. The first cell animation project I worked on was in 1972, it was 8 seconds and it took three of us 10 days to complete. The last character animation thing I did was just the Puppet Pin tool applied to some characters drawn in Illustrator and a little bit of Audio To Keyframes to time some of the animation. The whole project was almost 5 minutes long and it took me about 20 hours.