I need some simple layman explanation

Respectfully, if you're not a technical person you probably should not be attempting to install a EPM system into SharePoint. This stuff can be inherently quite complex and can't typically be boiled down to a series of simple steps for a layperson. Every action you take when configuring something like this has ramifications that must be considered and understood before implementation otherwise there can be unpleasant consequences, up to and including leaving SharePoint vulnerable to breach.

I strongly recommend that you seek support from the product vendor or other qualified assistance to get this product up and running. Most of the questions you are asking are particular to the product you're trying to install, so no one in a general SharePoint forum like this is going to be able to provide you with product-specific advice.

With that out of the way, you will definitely want to check with your vendor to make sure this EPM product is still active and viable, as https://learn.microsoft.com/en-us/sharepoint/dev/sp-add-ins/retirement-announcement-for-add-ins 

Good luck.