In the Accounts Side Menu you will see a list of the segments that you have access to. Any segments you create for your own use, you will want to save into the My Segments section. Why?
You can access the updated/live segments with one click rather than create them from scratch each time.
You can configure alerts to notify of changes to these segments.
You can trigger Playbooks for Accounts/Contacts entering a segment.
To save a segment (see video below)..
Once you have configured a Segment to your satisfaction, click the Save This Segment link.
In the pop up, give the segment a name
There are 2 toggle options,
Share this Segment with your Team? If you choose Yes this Segment will appear in the Shared Segments section of the Accounts Sidebar Slider
Apply a Tag to these Accounts. Here you can crate a Tag name and add a Tag color, these will be applied to the Segment and accounts within the Segment.