I'd recommend starting with a good Instant Pot recipe that gives you clear instructions. In the case of a "dump recipe," you'll add all of the ingredients to the bottom of your stainless steel liner in Instant Pot, without turning it on first.
Once your ingredients are in the pot, check the clear silicone sealing ring in the lid to make sure that it's properly seated. I like to wiggle it with my fingers to make sure it's correctly around the metal ring in the lid, and that it has wiggle room so that it will expand and seal the pot.
Secure the lid and move the steam release valve to Sealing. It's normal for the steam release valve to feel loose-- it's not a big movement between the Venting and Sealing positions.
Select the "Manual" or "Pressure Cook" button (the name will vary depending on the model of your machine, but they do the same thing) then use the + or - buttons to set the cooking time. The Instant Pot automatically cooks on high pressure unless you manually change it or use one of the preset buttons.
After you set the time, it will take about 10 seconds for the screen to read "On." The screen will remain that way as the pot heats up, building steam pressure. You'll know the pot is pressurized when the floating valve in the lid pops up. The countdown for your cooking cycle should start shortly after that.
When the cooking cycle is complete, let the pressure naturally release (i.e. do nothing for at least 10 more minutes) or perform a "quick release" by moving the steam release valve to venting right away. A good recipe will let you know which method you need to do. Be sure to keep your hand to the side of the vent, rather than over the top, so you won't be burned by the hot steam coming out.
When the floating valve in the lid drops, it's safe to open the lid, because that means all of the pressure has been released from the pot. The lid should be easy to twist off, so never force the pot open.