To add a certain number of Lync users to certain client list, you can create a distribution group with the following options

1. The group scope should be universal
2. The group type will be Distribution.
3. You must include the e-mail address

Now when this group is created, you can add any number of users to it. I will add couple of users from Lync users

After adding the users that I wanted to add. Now I have to go to Lync server and force the Address book synchronization between GAL and Lync.

Wait about 5 mins to Clients to download latest updates and then you will be able to see the changes on the client list. If not you can force the clients to download the new updates by using GPO to force special registry value

This registry will be applied on the Clients

reg add HKLM\Software\Policies\Microsoft\Office\15.0\Lync /v GalDownloadInitialDelay /t REG_DWORD /d 0 /f

From here you can now see the changes on Lync's contact lists.