DESelect is installed as an Installed Package in your Salesforce Marketing Cloud instance.
The DESelect Support team will provide you with a one-click installation link after your contract is signed.
The details of the permissions the Installed Package requires are listed in the DESelect Security Documentation.
We will also install a set of demo data which can be used for training purposes, or just to familiarize yourself with the possibilities DESelect offers. A list of scenarios that can be performed with this demo data can be found here.