Tom Clancy's The Division

Skill mods are unlocked by purchasing the various upgrades for each wing of your Base of Operations. When you are inside the Abilities menu on the Skills tab, you can select the two Skills you would like equipped, and press to add a variation to them (if unlocked). The following upgrades to the BOO unlock skill mods (three each, so you'll need to buy at least four upgrades):

• Medical Wing: Hazmat Unit, Intensive Care, Quarantine
• Security Wing: Dark Zone Ops, Gunsmith, Supply Line
• Tech Wing: Field Engineering, Generators, Water Purification

To actually unlock the achievement, you simply need to equip ten different mods. You can unlock them all, then switch which one you have equipped ten different times right in a row, and it will unlock. You do not actually need to use the mod for it to count.

NOTE: It seems some people are not getting credit for this achievement, and as of right now there does not seem to be a root cause or fix available. I will update when more info is available.