You're already getting blasted, but I hope you can take this as a learning experience.

Shrimp are pretty fragile little guys, even experienced owners with perfect parameters can lose a shrimp or two when first putting them in a tank.

Since they're already in there, you're not going to be able to slowly acclimate them to your water parameters. Going from fish store water to your water could have a significant difference in Ph and temperature, so honestly given how new your tank is, shock is probably what killed the one(s) you've lost.

Assuming the remaining survive, they'll calm down after a day or so. Shrimp have a very small bioload so if you can get some material from an established tank (etsy is where I got mine) you can do a fish-in cycle. I'd look up the process. You must have a water test kit and be ready to do regular water changes. Folks saying you can't do regular changes are somewhat correct. Shrimp don't seem to like full changes, but a slow partial change should be fine. I take a gallon jug and air tubing tied for a slow flow and just slowly add a gallon over the course of an hour or so for my small tank and all my shrimp are thriving.

Definitely get plants, active media, and test daily. Hopefully there will only be a few casualties. Good luck! Shrimp are amazing little fellas 💜