This really straightforward segment includes every user who has visited your site. We really recommend having a segment of 'everyone' who visits your site, as it is very useful in Permutive Analytics for understanding the behaviour of your entire audience and also for calculating targetable impressions in DFP.
Using the Pageview Event
Every user has a pageview_event. To build the segment of 'Everyone', include users if they've had a pageview event: