Hey there! If you are in the multiplayer menu your tokens appear in the top right corner of the screen. You can use them by selecting whatever it is you'd want to unlock (a new Divisions, Basic Training skill, Weapon, Equipment, or Scorestreak) and then choose to use your token on the item. This will only work if you are a high enough level to unlock that particular item, however. Every rank you achieve in Multiplayer will earn you a Rank Unlock Token, and Items you have unlocked will remain unlocked until you enter Prestige. Your prestige tokens will also show up next to your unlock tokens when you earn them.
Hope that helps
If only we had some sort of booklet which explained stuff like this. Or even a digital version in game