You can mention your teammates on any record (candidate/company/contact/job) by adding the "@" symbol in the Notes section.
Your teammate will get an email notification with a link to the record you mentioned them on.
Important Note: They might need to mark this email as "Not Spam" the first time so that all future "Mentions" show up right in the inbox.
You can reply to this email directly to start an email thread with your teammate or you can click on "View Mention" button to be redirected to the record where this mention was added.
You can see the all "mentions" in the Notes section.
Hope this helps!
Happy Recruiting :)