Intro: I created this project to help configure the NPSP changes needed after downloading a SF Dev Org instance and then installing the NPSP package. I'm intending to automatically perform the steps found here (should be performed after NPSP install): https://powerofus.force.com/articles/Resource/NPSP-Post-Install-Checklist
1- If you don't have a fresh Dev Org setup, set one up here: https://developer.salesforce.com/signup
2- Install the NPSP from the AppExchange. After the install you would need to follow the Post Install Checklist (URL above) to configure things like Record Types, Stages, etc. I'm proposing you leverage Salesforce DX at this point to streamline this process.
3-