Although you can add these users to your Contacts list in the same way you add federated users, you won’t see presence information for them.
Other users sign in to a federated site by using their non-federated user ID (email address).
The search box is located in the Contacts list, under the Contacts icon, and in the Phone view, under the Phone icon.
You can search for the names of people or for a skill (job title), and then add them to your Contacts list, for example.
When you create a group in Lync, it's called a contact group because it organizes your contacts in groups that are meaningful to you.
For example, you can choose to show “friendly names” as opposed to email names or status details as opposed to only names.
If this is the case, use the format user(unfederated.com)@federatedcompany.com--for example, When you’ve found the contacts that you want, you can add them to a contact group so you can find them easily next time.
Lync automatically populates Frequent Contacts based on the 10 contacts with whom you most often have conversations.
You can also “pin” your most important contacts to the top of the group for quick access.
Lync pre-populates the pinned list with your team members.