As a MIB agent, you will need the most powerful and advanced weapons in the galaxy to battle against rogue Aliens. 

Weapons may be found by opening Weapon Capsules. Better Weapon Capsules will give you a better chance at unlocking rarer weapons. 

If you get the same Weapon, you'll receive additional Weapon cards. Once you collect enough cards. you'll be able to upgrade that Weapon in the Database, boosting that Weapon's stats! (Note, you will need to spend Credits for each upgrade to the next level.)

To collect new Aliens, simply capture them once on the map.