Titles are earned through natural progression of your gameplay. Anything like using first aid sprays, reviving teammates, killing zombies with weapons or melee attacks, dying, even just walking and running will work towards your titles.
Play through a chapter or two on any campaign and you should have enough. Go to play game and choose the DOG TAGS menu then your achievement should unlock. If not you can look at the title menu to see which ones you are close to completing.