Combining a bit of backstory with new PvE content, Overwatch's Uprising update/event introduced a new objective based mode that lets you take on the roles of some of the original Overwatch members as they attempt to put down an uprising by Null Sector Omnics in King's Row. As a more substantial successor to the successful Halloween event, Uprising offers more than just a wave defense scenario with a few bosses sprinkled in between hordes of Zomnics. On top of that, it gives Torbjorn an opportunity to actually contribute to a game for once without being dead half the time.
Uprising starts off as you might expect: Torbjorn, Reinhardt, Mercy, and Tracer have to capture three zones in King's Row to disable the Omnic Anti-aircraft guns so that the next part of their plan can commence, much like your average 2-checkpoint match of Overwatch. The first point is located in a garage, the second is located in the open courtyard at the feet of where the King's Row statue normally would be, and the third point is inside the church. Fortunately, you only have to capture these points one at a time, and you can be revived upon death, so this should be a fairly simple task. As of this stage, you are fighting basic gun wielding Omnics, dubbed Nulltroopers, and slightly more threatening Eradicators, essentially bigger Nulltroopers with shields, who shouldn't be too much of a challenge; all Heroes are essentially free to do whatever they want within reason.
The second stage bears more of a resemblance to Overwatch's escort the payload gametype. After your team clears all three points and regroups at the designated area, a payload arrives and you must defend it as it powers up and moves down the street to the Omnic gates. It is here that Bastion units start spawning in alongside some more specialized Omnic units that are designed specifically to destroy the payload, Detonators (giant balls that explode) and Slicers (raptors with laser eyes). You can deal with these threats as you see fit, but it should be noted that for maximum efficiency, Reinhardt should just shield the payload while Tracer and Torbjorn's turret (Mercy can help too!) do most of the work. While it is true that Reinhardt can go crazy and swing away at everything, this is less viable at higher difficulties since Bastion can still mow down Reinhardt (and for that matter, the rest of the team) if he's careless; plus the first half of this stage is timed and does not progress any faster based on how many Omnics you kill.
After the payload reaches the gates, you and your team have to kill all of the OR-14 units (reskinned Orisas) in the final area of King's Row. This sounds simple, but there are Bastion units in the area, so it might be best if you and your team advance with a mild degree of caution, moving up to each OR-14 after Torbjorn finishes setting up his turret for support. Granted, the OR-14s have deployable barriers that mitigate the damage that Torbjorn's turrets can do, but it is a far better option than running into a chokepoint while the various Bastion units in the area slaughter you from their flanking positions. Ideally, Tracer should have her Pulse Bomb at the ready to flank the Bastion units, which are always located to the sides of the main lane, once Reinhardt draws their attention. It should be noted that the final pair of OR-14s will be fighting side by side while a couple of Bastions support them from behind, so plan the use of your Ultimate abilities accordingly. Thankfully, the OR-14s aren't especially damaging, so you can focus on the standard Omnics first to make it easier for Mercy to keep up with all the other damage your team will inevitably take.
Once the final OR-14 falls, you can kick back, relax, and enjoy your free(ish) Loot Boxes containing all the duplicate Sprays and Player Icons that you could ever ask for.