Hi! First of all, thank you for downloading our asset packs :)!
Almost all of the assets that we offer on the tortor-collective page are free.
On every page, you'll find information about the licensing and the credits. I advise you to take a look at that on every assets you are using for your game.
You'll usually find the information in the section called "More information". It's at the bottom of every pages on itch. For this specific pack, you can see the licensing : creative commons, non commercial use.
For the credits you can simply credit the Authors. But if the author of the pack stated to credit someone else explicitly, you'll have to credit this person.
For this specific pack for example, I stated that the users should put Intelligent System in their credits. So you can credit me, but most importantly, you'll have to credit Intelligent System.
The best way with to be safe with the copyright things is to read the information about licensing thoroughly, and if you have any doubts, contact the author directly, just as you did here :)
Good luck with your development! I hope this helped. And don't hesitate to share your work with us, in the comment sections.