Proving Ground Trials in Borderlands 3 are late-game activities that players can grind to get plenty of loot. You cannot get access to them until you have finished the main campaign, as you need an Eridian Analyzer to figure out where they are. This is a reward from playing the campaign, so if you are not quite there yet, just keep plugging away at the story.
The different Trials play out like dungeons. You will need to explore the area, fight lots of enemies, and take on a final boss that you need to defeat to finish the Trial.
To find the Trial of Survival, you first need to head for Devil’s Razor on Pandora. Go to the point marked on the map below, and you will find a strange plinth. Interacting with it will get your some coordinates, and you must then return to the Sanctuary and enter them into the navigation console. Simple spawn at Boomtown, then jump over the back wall and follow the road until you reach a bridge. Jump off the bridge and head into the cave system to get to the plinth.
When you get close to the plinth, a yellow exclamation mark will appear on the map, showing you exactly where it is.
Now you will be able to travel to the Trial of Survival, and use the drop pod to get to it. From that point on, the location will be in the map select under the name “Gradient of Dawn”, and you can travel there anytime you wish to take part in the Trial of Survival. When you first get there, you will find an NPC. Speak to them and you can then take on the Trial.