To merge a contact list first click on your Username on the top right of AdvisorStream, then click "Contacts".
Select the contact list you want to merge.
Click "Add all contact to list"
Select the list you want to merge with.
Click on the blue "OK" to confirm the merge. (Checkmark “Remove these contacts” if you want to remove the contacts from the original list).
(Note that if a contact is within multiple contact lists they will only receive the email or newsletter once)