On the sidebar, select Intranet → Agent Roster.
In the search table, you can click on an agent's name or the view button in the last column to view their bio.
It will still show their contact information if they do not have a bio.
This is an example of what an agent bio would look like.
Brokerage Managers can configure an agent's Bio in Setup > Accounts.
Each user can create or modify their own Bio in My Profile.