There aren't characters, per se, to level up in SW2, more like save files. And once you level your Wang up (hehe) to level 10, this achievement will pop. You get karma (xp) for kills and completing missions, so just play the game to level. There are also weapon upgrades that you can equip and also a skill you can unlock early to increase karma gained to level quicker. You will need to invest skill points into the skill though, and I'm not sure that you can respec your stats in this game, so you can make that call yourself.