As you and your team members sign in and start syncing your data, you'll start to see your All People and All Organizations directories magically populate with contacts you've had email/calendar communications with (see Syncing data with Affinity).
Here is a quick overview of the All People and All Organizations Directories.
Now, you can start leveraging these directories to quickly filter by Location, Job Titles, and other fields to narrow down your focus to specific people or organizations, then bulk-add them to a list (see How to copy list entries from one list to another).
Not sure what list type to choose from? See Types of Lists in Affinity.