The "POINTS SHARING" link is live under the REWARDS section (just under the Profile and Settings "Gear") of the Summit card holder's alaskaair.com account.
You can then choose another ATMOS member to share miles with you (at no charge) and send them an invitation.
The invitation gets sent to their email address on file, but...
Before clicking on ACCEPT INVITE in the email, make sure that user is already logged into his/her alaskaair.com account. Otherwise it will link to a blank alaskaair.com login page with no further dialogue.
Then, click the button to link accounts, and they can send any amount of available points to the main Summit card holder. The transfer can also go from the Summit card holder to the other member once accounts are linked. Transfers are initiated from the giver’s account.
The transfer happens within minutes and both members get emails to confirm. Worked for me tonight, but in theory should work once the POINTS SHARING tab appears in the Summit cardholder's account, even if the card has not been received yet.

This will only transfer RDP, not EQP to the Summit card holder. Up to 10 people can be linked at different times, but once a recipient is added, they must remain for 365 days.

Nice integration of a benefit previously held by Hawaiian credit card holders only for HawaiianMiles.