The Medal tracks the Mods Deployed statistic in the Building category of an agent's profile. Deploying a Mod that increases the stat to the next threshold awards the Medal immediately upon returning to the default Scanner view.
Engineer is a notoriously difficult Medal to obtain, requiring a huge number of Mods. While deploying the Mods is trivial, acquiring them is another story. At least 2,500,000 item rolls must be made to acquire all 50,000 Mods for Black Engineer, equivalent to over 800,000 perfect Glyph Hacks on L7 Portals!
As such, agents seeking Platinum or Black Engineer must enlist their fellow agents to feed them unwanted Mods. Capsules filled with Link Amps, Common Multi-Hacks, Common Shields, and Turrets are surprisingly powerful bartering chips for agents seeking Flip Cards, L8 XMP's, and other rare resources.