Here's my go-to method for cooking salmon in the Instant Pot. You can use fresh or frozen, and I've even included tips for cooking vegetables in the pot at the same time for a healthy dinner that's ready in less than 20 minutes.
Pour a cup of water into the Instant Pot and arrange the metal trivet on top. Place the salmon fillets into a single layer on the trivet and sprinkle them generously with salt and pepper.
Secure the lid and turn the pressure release valve to sealing. Use the manual setting to cook on high pressure for 3 minutes. (If using frozen fish fillets, cook them on high pressure for 5 minutes instead. No need to thaw.)
When the cooking cycle has completed, quickly turn the pressure release valve to venting to release the pressure. Serve the fish warm with your favorite sauce and side dish. (See the notes in my post above for cooking vegetables with the fish.)