Forging is one of the new crafting skills that together will gradually replace Mechanical Lore. Forging went live in Prime with the release of DR 3.0 in January 2013. The disciplines in the forging craft, Blacksmithing, Weaponsmithing, and Armorsmithing were introduced earlier and worked off of Mech Lore prior to DR 3.0's release.
Forging requires large, stationary tools to practice, such as a crucible and an anvil, in addition to hand-held tools. There are several places in the realms that are equipped for forgers and open to the public: the Riverhaven Forging Society, Crossing Forging Society, Shard Forging Society, Rathan Forging Society, Mer'Kresh Forging Society, the Hibarnhvidar Forging Society, Lava Forge and Iltesh Neg Degti Forge (Premium-only Leth Forge).
Experience is gained as a function of the difficulty of a given task at your skill particular skill level. If items of one tier of difficulty don't lend any experience you can try working with a more difficult material or the next higher tier of difficulty.